PUT vs. POST in REST

4 664

2 063

According to the HTTP/1.1 Spec:

The POST method is used to request that the origin server accept the entity enclosed in the request as a new subordinate of the resource identified by the Request-URI in the Request-Line

In other words, POST is used to create.

The PUT method requests that the enclosed entity be stored under the supplied Request-URI. If the Request-URI refers to an already existing resource, the enclosed entity SHOULD be considered as a modified version of the one residing on the origin server. If the Request-URI does not point to an existing resource, and that URI is capable of being defined as a new resource by the requesting user agent, the origin server can create the resource with that URI."

That is, PUT is used to create or update.

So, which one should be used to create a resource? Or one needs to support both?

alex

Posted 2009-03-10T14:25:20.390

Reputation: 29 878

13

Just to bring @MarkNottingham's comment to the latest revision, here's POST and PUT, as defined on HTTPbis.

– Marius Butuc – 2012-11-18T01:58:46.610

32It seems to me that this debate has arisen from the common practice of oversimplifying REST by describing the HTTP Methods in terms of CRUD operations. – Stuporman – 2013-02-14T17:05:15.023

5

Unfortunally the first answers are wrong about POST. Check my answer for a better explanation of the differences: http://stackoverflow.com/a/18243587/2458234

– 7hi4g0 – 2013-11-25T05:21:37.793

22

PUT and POST are both unsafe methods. However, PUT is idempotent, while POST is not. - See more at: http://restcookbook.com/HTTP%20Methods/put-vs-post/#sthash.u3S9tnPo.dpuf

– Dinesh Saini – 2014-01-10T20:26:49.143

2you know... I realise the spec refers to PUT as 'update', but I think everyone would be a lot less confused if we said it 'replaced', that is what it does after all. – thecoshman – 2014-06-15T20:28:54.743

1

In pratice, POST works well for creating resources. The URL of the newly created resource should be returned in the Location response header. PUT should be used for updating a resource completely. Please understand that these are the best practices when designing a RESTful API. HTTP specification as such does not restrict using PUT/POST with a few restrictions for creating/updating resources. Take a look at http://techoctave.com/c7/posts/71-twitter-rest-api-dissected that summarizes the best practices.

– java_geek – 2014-10-06T06:42:08.990

1idempotency is the key. Read PUT or POST: The REST of the Story by John Calcote. If your method is idempotent, go with PUT. If not go with POST. – Lijo – 2016-08-11T18:12:54.767

I don't understand the prevailing wisdom on this. OP's citation for PUT begins with "The PUT method requests that the enclosed entity be stored...." That screams "creation" to me. When we talk about "putting" something somewhere, we're talking about a place it hadn't been previously. You don't "put" something to change it. When you amend a document, you don't "put" a new one. The use of the HTTP verb PUT to mean "update" is an ill semantic fit. – Keith Tyler – 2017-03-28T16:31:30.537

PUT began as a way for early Microsoft HTML design tools to publish content directly to a server. The fact that it was also used to update (wholesale) was due to the lack of another updating method. Even still since it was a wholesale update, it really was creation, just one that was idempotent. An "update" implies that some aspect of the previous state was maintained. – Keith Tyler – 2017-03-28T16:33:03.800

Real world scenario in elastic documentation: https://www.elastic.co/guide/en/elasticsearch/reference/current/_modifying_your_data.html. Have a look at difference between all PUT requests and last POST request example.

– DevDio – 2018-04-10T09:02:12.047

The JavaBrains explains it very clealy. Have a look https://www.youtube.com/watch?v=rhTkRK53XdQ

– MAC – 2018-08-17T15:32:02.643

Difference between POST vs PUT methods should be described in defined context. Such as here, question is about REST, and it is actually about consistency and uniform interface. Till the time, you are honoring the API design consistency, you are good.

– lokesh – 2018-08-17T18:22:08.770

43

It may be helpful to use the definitions in HTTPbis - Roy put a fair amount of work into clarifying them. See: http://tools.ietf.org/html/draft-ietf-httpbis-p2-semantics-16#section-7.5

– Mark Nottingham – 2011-10-23T21:03:06.410

Answers

3 672

Overall:

Both PUT and POST can be used for creating.

You have to ask "what are you performing the action to?" to distinguish what you should be using. Let's assume you're designing an API for asking questions. If you want to use POST then you would do that to a list of questions. If you want to use PUT then you would do that to a particular question.

Great both can be used, so which one should I use in my RESTful design:

You do not need to support both PUT and POST.

Which is used is left up to you. But just remember to use the right one depending on what object you are referencing in the request.

Some considerations:

  • Do you name your URL objects you create explicitly, or let the server decide? If you name them then use PUT. If you let the server decide then use POST.
  • PUT is idempotent, so if you PUT an object twice, it has no effect. This is a nice property, so I would use PUT when possible.
  • You can update or create a resource with PUT with the same object URL
  • With POST you can have 2 requests coming in at the same time making modifications to a URL, and they may update different parts of the object.

An example:

I wrote the following as part of another answer on SO regarding this:

POST:

Used to modify and update a resource

POST /questions/<existing_question> HTTP/1.1
Host: www.example.com/

Note that the following is an error:

POST /questions/<new_question> HTTP/1.1
Host: www.example.com/

If the URL is not yet created, you should not be using POST to create it while specifying the name. This should result in a 'resource not found' error because <new_question> does not exist yet. You should PUT the <new_question> resource on the server first.

You could though do something like this to create a resources using POST:

POST /questions HTTP/1.1
Host: www.example.com/

Note that in this case the resource name is not specified, the new objects URL path would be returned to you.

PUT:

Used to create a resource, or overwrite it. While you specify the resources new URL.

For a new resource:

PUT /questions/<new_question> HTTP/1.1
Host: www.example.com/

To overwrite an existing resource:

PUT /questions/<existing_question> HTTP/1.1
Host: www.example.com/

Brian R. Bondy

Posted 2009-03-10T14:25:20.390

Reputation: 249 136

69@Jörg W Mittag: Not necessary. The second time could return 409 Conflict or something if the request has been modified in meantime (by some other user or the first request itself, which got through). – Mitar – 2011-11-27T23:28:22.697

2I think there is no difference in definition. 409 Conflict could be a result even for the first request the client made. In any case it should investigate the problem. – Mitar – 2011-11-28T02:21:32.723

546If I'm not mistaken, what we should be stressing is that PUT is defined to be idempotent. You still have to write your server in such a way that PUT behaves correctly, yes? Perhaps it's better to say "PUT causes the transport to assume idempotence, which may affect behavior of the transport, e.g. caching." – Ian Ni-Lewis – 2011-12-28T02:05:20.573

There are some ideas about how to make POST more reliable on Paul Prescod's website, though the site overall doesn't seem to be kept up to date.

– hotshot309 – 2012-04-04T18:48:51.177

5To make things even clearer it might be an idea to add that this example should return an error:

PUT /questions HTTP/1.1 Host: wahteverblahblah.com – Martin Brown – 2013-10-04T08:46:51.573

2I second that, @MartinBrown... your point is quite illuminating for me, actually. The answer as it stands is already fantastic, though, don't get me wrong! – Eric Fuller – 2013-10-23T03:57:52.370

128@JörgWMittag Idempotence catchphrase? How about "Send and send and send my friend, it makes no difference in the end." – James Beninger – 2014-03-03T17:13:28.320

7

PUT should only be used to create a resource if the client cares about the resource's name. A client caring about a resource's name indicates coupling. Coupling is the result of poor practices. Therefore, use POST. If there is concern about a resource being created twice with POST (since it's not idempotent) read this answer.

– Joshcodes – 2014-03-17T19:00:28.413

@JörgWMittag If a PUT is idempotent, what happens if the PUT is creating a new resource and the server is the one generating the object id? That would imply every PUT call would create a different object id. Does that mean that a PUT should not/cannot be used in that case, and a POST is required instead? – Eric B. – 2014-07-09T04:37:07.893

@EricB. The "object ID" is what he is referring to as the name. Thus, it should be supplied as part of the URL when using POST and not be generated by the server. – Legogris – 2014-09-22T07:28:37.093

1In pratice, POST works well for creating resources. The URL of the newly created resource should be returned in the Location response header. PUT should be used for updating a resource completely. Please understand that these are the best practices when designing a RESTful API. HTTP specification as such does not restrict using PUT/POST with a few restrictions for creating/updating resources – java_geek – 2014-10-06T06:28:04.227

1Great, according to your answer, both PUT and POST can be used to create and modify resources. So which one should be used or both must be supported for both create and update? – alex – 2009-03-10T15:06:30.243

1@alex: I updated my answer to give more detail in the section "Great both can be used, so which one should I use in my RESTful design:" – Brian R. Bondy – 2009-03-10T15:09:12.013

900I think one cannot stress enough the fact that PUT is idempotent: if the network is botched and the client is not sure whether his request made it through, it can just send it a second (or 100th) time, and it is guaranteed by the HTTP spec that this has exactly the same effect as sending once. – Jörg W Mittag – 2009-03-10T15:17:07.830

One note on using POST for CRUD style updates: I know that Roy Fielding pointed out that it should be more important for a RESTful design to make use of Hypermedia and discoverable self-explaining APIs than (e.g.) disallowing POST requests to perform item updates. But the quoted http spec gives a rule of thumb: In general it is quite intuitive and consistent to allow POST only for creating new subordinates for the given resource. For replacing or updating existing resources, I always prefer PUT or PATCH.

– matthias – 2015-03-12T18:01:06.430

Whatever the semantic value of POST vs PUT: If you have to support IE9 and IE8, beware that CORS requests in these versions do not support PUT - only GET/POST. See http://blogs.msdn.com/b/ieinternals/archive/2010/05/13/xdomainrequest-restrictions-limitations-and-workarounds.aspx

– flexponsive – 2015-04-10T19:21:14.070

2Can someone elaborate on this sentence. "With POST you can have 2 requests coming in at the same time making modifications to a URL, and they may update different parts of the object." Please explain why this applies to POST and not to PUT? – Kevin Wheeler – 2015-09-08T22:28:18.443

1

@KevinWheeler: Bill de Hora has a good blog post about using POST to update only some fields of a resource, while PUT must supply all fields (whether creating or updating): http://www.dehora.net/journal/2009/02/03/just-use-post/ He makes the point that PUT can be very heavy weight if you have to send through all the fields when you only want to update one. So, following his scheme, you could have POST sending through an update to a couple of fields and another POST request updating another couple of fields in the same resource. Not sure but I think PATCH now does the same sort of thing.

– Simon Tewsi – 2016-01-13T21:31:05.730

3modify and update what is the difference – Premraj – 2016-01-30T00:19:25.007

17Thinks of them as: PUT = insert or update; POST = insert. So when you make two PUT - you get the one new record, when you do two POSTs - you get two new records. – Eugen Konkov – 2016-08-22T09:34:34.823

"With POST you can have 2 requests coming in at the same time making modifications to a URL, and they may update different parts of the object." .......... you mean POST can update? – Raúl – 2016-11-11T07:03:20.273

"Used to modify and update a resource" ....... you must meant 'or' here - right ? – Raúl – 2016-11-11T07:04:15.313

@Learner I second your sentiment. This answer and the examples are confusing. Words are used inconsistently. – lucid_dreamer – 2017-06-18T01:52:52.233

Think like a server: Expect an item to be uniquely identifiable. If I receive a PUT without an identifier I'm going to reject it because it's not telling me what to update. If I receive a POST with an identifier I'm going to reject it because I can't create what already exists. – Brian Lowe – 2017-07-20T13:16:25.667

Assuming I having the following URL: test.awesome.com/questions, is the above saying that I would PUT to that URL to create a new resource? I thought it's POST to a collection and PUT to a URL with a specified ID. Isn't it PUT here: test.awesome.com/questions/1 and POST here: test.awesome.com/questions? Or, is it saying if test.awesome.com/questions/1 doesn't exist, PUT will create it or replace it if it already exists on the server? – cloudstrifebro – 2017-09-22T16:11:22.863

Does idempotency of PUT mean we cannot have the same resource name or that objects that have the same hashes cannot exist at the same time ? – wedran – 2017-11-21T19:56:01.283

@wedran idempotency means, that if someone calls PUT once or multiple times, the outcome is still the same. So an operation, where every call causes a change (e.g. a counter to increment) wouldn't be idempotent ( http://www.restapitutorial.com/lessons/idempotency.html ). I would recommend reading through all answers answers here to get a better understanding. It doesn't have anything to do with the resource name or a hash.

– skofgar – 2017-11-21T23:02:51.397

Am I mistaken, or does this answer contradict the info in the question? There it says Post=Create. Put=Update if possible. If not, create. However here, it says 'Post=Update'. I'm confused. – MarqueIV – 2017-12-15T21:43:41.483

2You should really be using PATCH to update a entity, PUT to insert a entity , DELETE to delete/remove a entity and a POST to do other things, like submitting form data type requests. – SynackSA – 2018-01-19T19:03:34.703

Would be nice if we could add the difference with PATCH. Right now I'm in a situation where I define the resource's ID beforehand (not the server), I'm therefore using PUT to create it, and then POST to update it, but I could also use PATCH instead of POST and that would make more sense, semantically speaking. – Vadorequest – 2018-02-20T00:49:25.907

POST can't be used to update, please, read RFC 7231. – Sirius – 2018-02-20T11:03:29.737

@BrianR.Bondy you Wrote: _POST: Used to modify and update a resource POST /questions/<existingquestion> HTTP/1.1. But in this case you make POST method idempotent. This is in contrast with HTTP specification! RFC 7231

– Glauco Cucchiar – 2018-03-02T10:50:40.853

@BrianR.Bondy in the below link definitions are contradictory https://restfulapi.net/rest-put-vs-post/

– PPB – 2018-04-10T12:00:39.937

@Sirius - I thought the same thing, but technically POST can be used to append to an existing resource as stated in Section 4.3.3 of RFC 7231 - 4th bullet point. I would consider appending as an update but it could be interpreted differently

– commandt – 2018-05-03T18:36:55.397

"You do not need to support both PUT and POST," is followed by, "If the URL is not yet created, you should not be using POST to create it while specifying the name... You should PUT the <new_question> resource on the server first." Perhaps, "You do not need to support POST if you support PUT"? Or is @SynackSA on to something?

– ruffin – 2018-08-30T14:05:20.147

does idempotent mean that if a ressource already exist and is similar the PUT method preserve some ressource by overcome the point and go directly to the next point ? A kind of optimize save in other word – Webman – 2018-09-03T00:44:08.607

what if I only use POST for both updates and create? can it cause any problem in action? – Mohammad Salehi – 2018-09-04T19:18:00.093

1Isn't author's claim that POST can be used to modify/update incorrect? For example he is using POST /questions/&lt;existing_question&gt; which means that the POST request is aware of the location of the resource which is &lt;existing_question&gt; but this means POST is showing idempotent behavior cause no matter how many time we make this request the same resource(&lt;existing_question&gt;) will be accessed at the server which is not correct as POST is supposed to be non-idempotent which means every time we invoke this it should change the state of the server. – Yug Singh – 2018-09-30T19:48:51.190

1 955

You can find assertions on the web that say

Neither is quite right.


Better is to choose between PUT and POST based on idempotence of the action.

PUT implies putting a resource - completely replacing whatever is available at the given URL with a different thing. By definition, a PUT is idempotent. Do it as many times as you like, and the result is the same. x=5 is idempotent. You can PUT a resource whether it previously exists, or not (eg, to Create, or to Update)!

POST updates a resource, adds a subsidiary resource, or causes a change. A POST is not idempotent, in the way that x++ is not idempotent.


By this argument, PUT is for creating when you know the URL of the thing you will create. POST can be used to create when you know the URL of the "factory" or manager for the category of things you want to create.

so:

POST /expense-report

or:

PUT  /expense-report/10929

Cheeso

Posted 2009-03-10T14:25:20.390

Reputation: 133 327

22@Schneider, in this case your server is making an extra effort to guarantee idempotence, but it is not advertising it. Browsers will still warn the user if they try to reload such a POST request. – Tobu – 2012-01-06T10:53:35.883

42@Schneider POST may create a subsidiary resource; hence you can POST to collection, like POST /expense-reports and it would create as many entities (expense reports) on your server as the quantity of requests you've sent, even if they are completely similar. Think of it as inserting the same row in the DB table (/expense-reports) with auto-incremented primary key. Data remains the same, key (URI in this case) is generated by server and is different for every other insert (request). So, POST effect can be idempotent, but also may not. Hence, POST is not idempotent. – Snifff – 2012-01-26T17:32:20.700

3This is dead on, and the "accepted" answers look to me (@brian) to miss this critical subtlety. – Andrew Roberts – 2012-03-21T18:48:59.243

11Let's say we have entities which may have two properties - name and date. If we have an entity with an existing name and date, but then make requests to it specifying only a name, the proper behavior of PUT would be to obliterate the date of the entity, whereas POST may update only the properties specified, leaving the unspecified properties as they were before the request was made.

Does that sound correct/reasonable, or is it an improper use of PUT (I saw references to PATCH, which it seems would be more appropriate, but doesn't exist yet)? – Jon z – 2013-05-08T18:28:14.130

This is dead wrong. Idempotence should not decide if PUT or POST is used. Who owns the responsibility for the URL structure decides if PUT or POST is used. To understand how to handle duplicate POST requests see this answer.

– Joshcodes – 2014-04-24T12:22:17.217

60I agree, wherever idempotence is concerned it should trump any other concerns since getting that wrong can cause many many unexpected bugs. – Josh – 2010-10-26T05:56:09.320

1I wonder if what he means by "POST can update a resource" is that by POSTing to a collection you are adding an item to it and therefore "updating the collection". That distinction seems a bit misleading. I like the answer, though. – Thomas – 2015-05-28T13:43:21.590

1Thank you, this is very helpful. To further your analogy, POST may be used to "assign" (as opposed to x++), but it's more like obj.setX(5) -- the setX method should result in x being 5, but may have side effects. – Nicole – 2015-10-01T22:21:12.873

If using POST to partially update an existing resource, such as updating only a couple of fields, can you specify the resource name? The reason I ask is that many people say POST can't be used with an individual resource, only with its parent collection. eg POST applied to expense reports. Is it possible to update say a single field of expense report 10929 using POST /expense-report/10929 ? – Simon Tewsi – 2016-01-13T21:39:17.277

2Yes. In fact, AtomPub protocol defies this (or more accurately, restricts its semantic meaning of PUT): "PUT is used to edit a known Resource. It is not used for Resource creation." Just because AtomPub protocol says so (which is valid by the way) doesn't mean all RESTful protocols must follow it. (because REST is generic) – Hendy Irawan – 2011-04-14T16:04:01.447

I agree with this answer. Key difference is idempotency of PUT. I found a very good explanation of idempotency at https://stormpath.com/blog/put-or-post

– Naymesh Mistry – 2016-09-05T02:01:43.107

13If POST can update a resource, how is that not idempotent? If I change a students age using PUT and do that 10x times the students age is the same if I did it once. – Schneider – 2011-05-06T10:54:35.800

@Cheeso: First stament is quite right – Learner – 2016-11-09T01:14:55.757

I don't know but somehow I agree with this answer. It makes more sense to me – Parag Meshram – 2017-02-16T05:18:33.947

2Comparing PUT and POST to mysql: POST is like an INSERT INTO without providing the ID of an auto-increment column, if you do it multiple times, you will create multiple rows. PUT is like an UPDATE using the primary key in the WHERE statement, if you do it multiple times, the row should be the same after each one. Some vendors may also allow you to PUT to create, which would be like an INSERT INTO providing a value for the auto-increment column. – Jo. – 2017-03-16T19:01:14.657

There is nothing that says you cannot implement POST to be idempotent, all the standard says is that it is treated as unsafe. Implenting an idempotent post for resource creation where the client can generate the id and pass along a request token to identify retries works well.. eg /api/foobars/{GUID}?request={AnotherGUID} – nrjohnstone – 2017-08-20T18:16:59.153

Is there anything in any of modern web servers, that makes the claim about the 'idempodence' of PUT valid? In other words, can I expect that if client sends 2 identical PUT requests, my server code might receive only one of them? – 9ilsdx 9rvj 0lo – 2017-09-04T10:10:01.133

@Jo. That was the best explanation for using PUT vs POST for me. Also, Nigel Thornes answer expands on that with PATCH. – JoeMoe1984 – 2018-05-25T16:58:38.883

591

  • POST to a URL creates a child resource at a server defined URL.
  • PUT to a URL creates/replaces the resource in its entirety at the client defined URL.
  • PATCH to a URL updates part of the resource at that client defined URL.

The relevant specification for PUT and POST is RFC 2616 §9.5ff.

POST creates a child resource, so POST to /items creates a resources that lives under the /items resource. Eg. /items/1. Sending the same post packet twice will create two resources.

PUT is for creating or replacing a resource at a URL known by the client.

Therefore: PUT is only a candidate for CREATE where the client already knows the url before the resource is created. Eg. /blogs/nigel/entry/when_to_use_post_vs_put as the title is used as the resource key

PUT replaces the resource at the known url if it already exists, so sending the same request twice has no effect. In other words, calls to PUT are idempotent.

The RFC reads like this:

The fundamental difference between the POST and PUT requests is reflected in the different meaning of the Request-URI. The URI in a POST request identifies the resource that will handle the enclosed entity. That resource might be a data-accepting process, a gateway to some other protocol, or a separate entity that accepts annotations. In contrast, the URI in a PUT request identifies the entity enclosed with the request -- the user agent knows what URI is intended and the server MUST NOT attempt to apply the request to some other resource. If the server desires that the request be applied to a different URI,

Note: PUT has mostly been used to update resources (by replacing them in their entireties), but recently there is movement towards using PATCH for updating existing resources, as PUT specifies that it replaces the whole resource. RFC 5789.

Update 2018: There is a case that can be made to avoid PUT. See "REST without PUT"

With “REST without PUT” technique, the idea is that consumers are forced to post new 'nounified' request resources. As discussed earlier, changing a customer’s mailing address is a POST to a new “ChangeOfAddress” resource, not a PUT of a “Customer” resource with a different mailing address field value.

taken from REST API Design - Resource Modeling by Prakash Subramaniam of Thoughtworks

This forces the API to avoid state transition problems with multiple clients updating a single resource, and matches more nicely with event sourcing and CQRS. When the work is done asynchronously, POSTing the transformation and waiting for it to be applied seems appropriate.

Nigel Thorne

Posted 2009-03-10T14:25:20.390

Reputation: 16 012

46Or from the other side of the fence: PUT if the client determines the resulting resource's address, POST if the server does it. – DanMan – 2012-11-28T19:47:28.800

3I think that this answer should be edited to make it more clear what @DanMan pointed in a very simple way. What I find the most valuable here is the note at the end, stating that a PUT should be used only for replacing the whole resource. – Hermes – 2013-11-26T22:37:51.960

2PATCH isn't a realistic option for at least a few years, but I agree with the ideology. – crush – 2014-10-03T17:33:08.580

4I'm trying to understand, but using PUT to create something would only make sense if the client knows for sure that the resource doesn't exist yet, right? Following the blog example, say you have created hundreds of blog posts in a couple of years, then accidentally pick the same title as you did for a post two years ago. Now you have gone and replaced that post, which wasn't intended.

So using PUT to create would require the client to track what is taken and what is not, and could lead to accidents and unintended side effects, as well as having routes that do two entirely different things? – galaxyAbstractor – 2015-01-30T09:01:22.860

4You are correct. PUTting a blog post at the same url as an existing one would cause an update to that existing post (although you could obviously check first with a GET). This indicates why it would be a bad idea to use just the title as the URL. It would however work anywhere there was a natural key in the data... which in my experience is rare. Or if you used GUIDs – Nigel Thorne – 2015-02-03T05:20:12.390

2@crush: Why isn't PATCH a realistic option for at least a few years? – arthropod – 2016-06-21T03:58:59.933

@NigelThorne The only answer that talks about server defined and client defined URLs. Who does validation on client defined URLs? – realPK – 2016-07-26T22:17:19.527

1@PK_ the server validates the URL. The client would have to adhere to the url schema the server supports. Invalid urls would be rejected by the server. – Nigel Thorne – 2016-08-30T06:44:42.703

All of my doubts are cleared through this answer – C Sharper – 2017-02-28T06:40:29.650

I'm working on a project where the id's are known to the client. So I'd like to use PUT for creation. However, a colleague disagrees with the argument that it would be confusing if the resource would get deleted while someone else does a PUT (to update as a whole), now the resource would be recreated, even though it was deleted. His point is, that in a POST, PUT, DELETE scenario PUT should return a 404 if someone wants to update a resource and it doesn't exist. Any thoughts that might help? – skofgar – 2017-11-21T23:15:12.270

2HTTP says ... when a client 'puts' to a url, it is requesting that url to hold that data. It's up to the server to decide if it's happy to do that. If you want 'DELETE' to stop PUTs working... then that's fine, but can you ever have anything at that url ever again? If so, then you should probably let the subsequent PUT through... after all one of your users is trying to put content at that location for a reason. Who's to say who was more correct? :) the answer is.. "your domain". Do what models your domain. but PUT means "I am trying to store this here". – Nigel Thorne – 2017-11-22T06:47:53.323

@skofgar PUT is supposed to be idempotent (multiple identical requests have the same result.) That's a powerful concept and makes developers' lives infinitely easier because it's a reliable operation. I agree w/ the user confusion in that scenario, but I think you want to address that in the front end as much as possible. It's also not uncommon behavior and is sometimes very helpful (e.g. if editing in one browser tab, and you delete it in another by mistake, then saving restores the resource in its entirety) – John Neuhaus – 2018-05-14T15:41:18.090

176

Summary:

Create:

Can be performed with both PUT or POST in the following way:

PUT

Creates THE new resource with newResourceId as the identifier, under the /resources URI, or collection.

PUT /resources/<newResourceId> HTTP/1.1 

POST

Creates A new resource under the /resources URI, or collection. Usually the identifier is returned by the server.

POST /resources HTTP/1.1

Update:

Can only be performed with PUT in the following way:

PUT

Updates the resource with existingResourceId as the identifier, under the /resources URI, or collection.

PUT /resources/<existingResourceId> HTTP/1.1

Explanation:

When dealing with REST and URI as general, you have generic on the left and specific on the right. The generics are usually called collections and the more specific items can be called resource. Note that a resource can contain a collection.

Examples:

<-- generic -- specific -->

URI: website.com/users/john
website.com  - whole site
users        - collection of users
john         - item of the collection, or a resource

URI:website.com/users/john/posts/23
website.com  - whole site
users        - collection of users
john         - item of the collection, or a resource
posts        - collection of posts from john
23           - post from john with identifier 23, also a resource

When you use POST you are always refering to a collection, so whenever you say:

POST /users HTTP/1.1

you are posting a new user to the users collection.

If you go on and try something like this:

POST /users/john HTTP/1.1

it will work, but semantically you are saying that you want to add a resource to the john collection under the users collection.

Once you are using PUT you are refering to a resource or single item, possibly inside a collection. So when you say:

PUT /users/john HTTP/1.1

you are telling to the server update, or create if it doesn't exist, the john resource under the users collection.

Spec:

Let me highlight some important parts of the spec:

POST

The POST method is used to request that the origin server accept the entity enclosed in the request as a new subordinate of the resource identified by the Request-URI in the Request-Line

Hence, creates a new resource on a collection.

PUT

The PUT method requests that the enclosed entity be stored under the supplied Request-URI. If the Request-URI refers to an already existing resource, the enclosed entity SHOULD be considered as a modified version of the one residing on the origin server. If the Request-URI does not point to an existing resource, and that URI is capable of being defined as a new resource by the requesting user agent, the origin server can create the resource with that URI."

Hence, create or update based on existence of the resource.

Reference:

7hi4g0

Posted 2009-03-10T14:25:20.390

Reputation: 2 294

6This post was helpful to me in understanding that POST adds "something" as a child to the given collection (URI), whereas PUT explicitly defines the "something" at the given URI location. – kwah – 2013-11-23T16:33:19.810

It is a very reasonable way to implement a CRUD API that is REST/http complient. A good reading: the RFC about HTTP, and in particular what is idempotent and the expected behavior of web cache. The use of POST/PUT are constrained by the expected behavior of cache (web or user agent) – mcoolive – 2014-10-21T09:34:02.373

2This is the best answer, here, I think: none of this "POST can update a resource" nonsense. I like your statement, "Update can only be performed with PUT". – Thomas – 2015-05-28T13:44:40.013

1No, PUT is not for update or create. It is for replacing. Note that you can replace nothing with something for the effect of creating. – thecoshman – 2015-06-08T08:07:28.953

@thecoshman I have posted in my answer the relevant parts of the HTTP/1.1 spec. Read the last part of my answer entitled Spec. The spec clearly states that PUT is used to create or update an entity. – 7hi4g0 – 2015-06-08T12:50:09.287

1@7hi4g0 PUT is for for updating with a complete replacement, in other words, it replaces. You replace nothing with something, or something with a completely new something. PUT is not for making a minor change (unless you have the client make that minor change and provide the entire new version, even what is remaining the same). For partial modification, PATCH is the method of choice. – thecoshman – 2015-06-08T12:57:21.580

@thecoshman I never said that PUT should be used for partial modification. If you don't like the terminology, I can restate. The spec clearly states that PUT is used to create or modify an entity. – 7hi4g0 – 2015-06-08T13:07:40.117

@thecoshman I guess you can say, create or replace, but the two are different actions according to the Spec. Either way, update, modify, replace are only terms. – 7hi4g0 – 2015-06-08T13:15:34.170

@7hi4g0 my point is, if you read the rest of that sentence from the spec, you are updating that URI to have a completely new resource at that location. As such, it is replace 100% with what data is included in this PUT request. Likewise, I'd argue that create is effectively just replacing 'nothing with something'. And so, you can "Keep It Simple Stupid" by just saying "PUT is for replacing". – thecoshman – 2015-06-09T16:15:36.167

1@thecoshman You could, but it wouldn't be too clear that create is also covered in there. In this case, it is better to be explicit. – 7hi4g0 – 2015-06-09T20:21:12.220

@7hi4g0 I would generally say that POST is (usually) more appropriate for create, but still. I think we can leave it at that, we've at least given people sensible discussion to think about, which IMO is the most important thing to have when you have fluffy 'guideline' :P – thecoshman – 2015-06-09T21:37:49.250

PUT can be used to create a resource and is appropriate for creating resources if the client is responsible for providing the URL structure. However, it is highly unlikely that in your solution it is appropriate for the client to provide the URL structure. – Joshcodes – 2015-09-11T14:49:56.053

This was the most helpful resource by far showing the difference between PUT /users/John and POST /users/John. Thanks. – PRMan – 2018-06-30T18:40:48.183

Of course you can POST an 'update'. If you keep prior versions around (and there are many reasons why you may want to do so) then your update is not idempotent and so cannot be expressed by PUT. (Or in other words everything turns into a collection when you stare at it hard enough) – CurtainDog – 2018-09-05T06:20:49.970

IMHO this answer covers all the aspects of PUT vs POST compared to the accepted answer. First, it explains that POST only creates which is true as POST is supposed to be idempotent and PUT can create or update/modify. Secondly, collections is included in the answer which is important in REST. Thirdly, important parts regarding POST and PUT are picked up from the spec. – Yug Singh – 2018-09-30T20:44:03.410

161

I'd like to add my "pragmatic" advice. Use PUT when you know the "id" by which the object you are saving can be retrieved. Using PUT won't work too well if you need, say, a database generated id to be returned for you to do future lookups or updates.

So: To save an existing user, or one where the client generates the id and it's been verified that the id is unique:

PUT /user/12345 HTTP/1.1  <-- create the user providing the id 12345
Host: mydomain.com

GET /user/12345 HTTP/1.1  <-- return that user
Host: mydomain.com

Otherwise, use POST to initially create the object, and PUT to update the object:

POST /user HTTP/1.1   <--- create the user, server returns 12345
Host: mydomain.com

PUT /user/12345 HTTP/1.1  <--- update the user
Host: mydomain.com

ThaDon

Posted 2009-03-10T14:25:20.390

Reputation: 4 022

14Actually, it should be POST /users. (Note that /users is plural.) This has the affect of creating a new user and making it a child resource of the /users collection. – DavidRR – 2014-12-16T13:54:53.077

4@DavidRR to be fair, how to handle groups is another debate altogether. GET /users makes sense, it reads as you want, but I'd be ok with GET /user/&lt;id&gt; or POST /user (with payload for said new user) because it reads correctly 'get me users 5' is odd, but 'get me user 5' is more natural. I'd probably still fall down on the side of pluralisation though :) – thecoshman – 2015-06-08T07:57:14.830

151

POST means "create new" as in "Here is the input for creating a user, create it for me".

PUT means "insert, replace if already exists" as in "Here is the data for user 5".

You POST to example.com/users since you don't know the URL of the user yet, you want the server to create it.

You PUT to example.com/users/id since you want to replace/create a specific user.

POSTing twice with the same data means create two identical users with different ids. PUTing twice with the same data creates the user the first and updates him to the same state the second time (no changes). Since you end up with the same state after a PUT no matter how many times you perform it, it is said to be "equally potent" every time - idempotent. This is useful for automatically retrying requests. No more 'are you sure you want to resend' when you push the back button on the browser.

A general advice is to use POST when you need the server to be in control of URL generation of your resources. Use PUT otherwise. Prefer PUT over POST.

Alexander Torstling

Posted 2009-03-10T14:25:20.390

Reputation: 13 560

8Sloppiness may have cause it to be commonly taught that there are only two verbs you need: GET and POST. GET to obtain, POST to change. Even PUT and DELETE were performed using POST. Asking what PUT really means 25 years later maybe a sign we learned it wrong at first. REST popularity drove people back to the basics where we must now unlearn past bad mistakes. POST was overused and now commonly taught incorrectly. Best part: "POSTing twice with the same data means create two identical [resources]". Great point! – maxpolk – 2014-09-01T19:36:14.857

1How can you use PUT to create a record by the ID, like in your example user 5 if it doesn't exist yet? Don't you mean update, replace if already exists? or something – Luke – 2014-11-28T12:44:13.487

@Coulton: I meant what I wrote. You insert user 5 if you PUT to /users/5 and #5 does not exist yet. – Alexander Torstling – 2014-11-28T15:46:33.013

@Coulton: And PUT can also be used to replace the value of an existing resource in its entirety. – DavidRR – 2014-12-16T14:02:34.930

1"Prefer PUT over POST"... care to justify that? – thecoshman – 2015-06-08T08:04:31.713

@thecoshman: Sure. I wrote that as a general advise. My reasoning is that PUT is idempotent, hence better from a network perspective. POST is also more general, so by recommending PUT you avoid POST being used for situations where PUT would have sufficed. POST is also heavily overused due to browser restrictions, and so a recommendation against it will have positive effects for REST as a concept. There are also some positive effects in the URL scheme when the clients are in control of the URL construction IMO, but I cannot fit that into a comment here. – Alexander Torstling – 2015-06-08T09:08:54.123

@AlexanderTorstling excuse whilst I try to tease out solid reasoning others might benefit from. Better from a network perspective how? Sure if your network goes down and you failed to confirmation you can just re-create, but what if it did work, and then someone else modified? Your re-PUT will overwrite what they did. You make it sound like POST has some extra overhead compared to PUT (where PUT would have sufficed). I think the fact POST is overused should not mean we advise against it when it is the correct choice, just learn to advise the right choices. That Last point is rather subjective. – thecoshman – 2015-06-08T13:09:30.353

@thecoshman: I was thinking of retries, yes. PUT concurrency can be controlled by conditional headers like If-Modified et al. Doing the same for POST would result in much coarser locking. You have a point in advocating the right choices, I however had no intention of banning POST. Perhaps "Use PUT when possible" would have been a better wording? – Alexander Torstling – 2015-06-08T14:28:40.777

@AlexanderTorstling well, my main point was that your answer states you should have a preference, with no justification for it. Your responses here however seem fairly justifiable. That said, I don't think it's the correct reasoning to use for PUT vs POST – thecoshman – 2015-06-09T16:12:54.923

Here is one benefit that using POST to create a resource has over PUT. In this case, if you try to modify a resource that doesn't exist yet (using PUT), you will get an error. To generalize this advice beyond PUT vs POST, try to not to use an interface where the result/action depends on the current state, because the user may have an incorrect assumption about what the current state is (in the put example, he thinks the resource already exists). Use two separate interfaces and throw an error if the current state does not match the preconditions. – Kevin Wheeler – 2015-09-08T23:07:51.773

PS I still don't understand what is meant by "Better from a network perspective." I can, however, think of at least one reason on my own as to why PUT would be better from a network perspective: the results can be cached (perhaps by a proxy cache server). – Kevin Wheeler – 2015-09-08T23:10:46.073

I would say that POSTing twice with the same data MAY result in two identical users. Were I creating my API, if someone tried to POST a new user with the same email address, but different data, I might issue a 409. If someone tried to POST a new user with identical data, I might issue a 303. I probably wouldn't want my system to be able to have two identical users. – Dan Jones – 2015-12-27T16:24:57.363

I don't think this is true at least for App with database ... so if I have a POST /createUser/diego and PUT /createUser/jose , and I clicked twice and both with the method persisted() , it will insert 4 records. – diego matos - keke – 2016-03-16T22:58:26.393

@diegomatos-keke: You are not supposed to PUT or POST to a verb URI like "createUser". You are supposed to POST to '/users' to create Diego and PUT to '/users/diego' to update Diego. If you click twice for the POST, you will create 2 Diegos. But if you click twice for the PUT, you will update Diego twice, but not create 2 Diegos. – Alexander Torstling – 2016-03-17T08:42:32.043

@AlexanderTorstling commenting to point your attention to http://stackoverflow.com/questions/39057416/how-to-ignore-multiple-clicks-from-an-impatient-user. maybe you can help.

– Roam – 2016-08-20T19:23:05.193

114

Use POST to create, and PUT to update. That's how Ruby on Rails is doing it, anyway.

PUT    /items/1      #=> update
POST   /items        #=> create

Tim Sullivan

Posted 2009-03-10T14:25:20.390

Reputation: 13 248

4POST /items adds a new item to an already defined resource ('item'). It does not, as the answer says, "create a group." I don't understand why this has 12 votes. – David J. – 2012-06-21T05:26:07.290

Out of the box, Rails does not support 'creating a group' via REST. To 'create a group' by which I mean 'create a resource' you have to do it via the source code. – David J. – 2012-06-21T05:28:13.183

It has 12 votes because it predates the change that was made that added the group thing. I've reverted the change. – Tim Sullivan – 2012-06-21T15:20:37.243

8This is a fair guideline, but an oversimplification. As the other answers mention, either method could be used for both create and update. – Brad Koch – 2013-03-07T15:55:49.663

2I agree with the answer with a slight modification. Use POST to create and PUT to update the resource completely. For partial updates, we can use PUT or PATCH. Lets say we want to update the status of a group. We can use PUT /groups/1/status with the status is the request payload or PATCH /groups/1 with the details about the action in the payload – java_geek – 2014-10-06T06:26:04.967

@BradKoch You are right with the statement; but when you are designing a RESTful API, you need to ensure that its consistent so that it makes life easy for clients consuming your API's. If you are using POST/PUT interchangeably to create/update resources it makes life hard for your consumer. You would want to keep it easy for your clients because thats how you grow your consumer base. – java_geek – 2014-10-06T06:38:21.597

2It should also be made clear that PUT /items/42 is also valid for creating a resource, but only if the client has the privilege of naming the resource. (Does Rails allow a client this naming privilege?) – DavidRR – 2014-12-16T14:10:00.847

replace is better word for PUT patch is for update – Saurabh Chandra Patel – 2016-01-20T06:59:37.133

what about PATCH?

PATCH /items/1 ? – cegprakash – 2018-03-28T17:08:17.523

63

REST is a very high-level concept. In fact, it doesn't even mention HTTP at all!

If you have any doubts about how to implement REST in HTTP, you can always take a look at the Atom Publication Protocol (AtomPub) specification. AtomPub is a standard for writing RESTful webservices with HTTP that was developed by many HTTP and REST luminaries, with some input from Roy Fielding, the inventor of REST and (co-)inventor of HTTP himself.

In fact, you might even be able to use AtomPub directly. While it came out of the blogging community, it is in no way restricted to blogging: it is a generic protocol for RESTfully interacting with arbitrary (nested) collections of arbitrary resources via HTTP. If you can represent your application as a nested collection of resources, then you can just use AtomPub and not worry about whether to use PUT or POST, what HTTP Status Codes to return and all those details.

This is what AtomPub has to say about resource creation (section 9.2):

To add members to a Collection, clients send POST requests to the URI of the Collection.

Jörg W Mittag

Posted 2009-03-10T14:25:20.390

Reputation: 286 660

7There's nothing wrong with allowing PUT to create resources. Just be aware that it means that the client provides the URL. – Julian Reschke – 2010-04-07T07:47:32.017

5There's something very wrong with allowing PUT to create resources: the client provides the URL. That's the server's job! – Joshcodes – 2013-10-29T17:33:01.867

@Joshcodes It is not always the case that it is the server's job to create client ids. I have increasingly seen designs that let clients generate some sort of UUID as the resource id. This design lends itself in particular to increase scale. – Justin Ohms – 2017-02-05T18:26:16.980

@JustinOhms I agree with your point about client generated IDs (side note: all systems designed by me since circa 2008 require the client to create the ID as a UUID/Guid). That does not mean the client should specify the URL. – Joshcodes – 2017-02-06T18:24:26.610

@Joshcodes It's matter of separating concerns. Where the URL is generated is actually of little consequence. Yes the server is responsible for delivering content from the correct URL but that does not limit a server from responding to a request on an incorrect URL. The correct response from the server in this case is a 308. A proper client will then retry the PUT on the correct URL. Another example is a distributed system where not all nodes know of all resource provided by clients. Here a PUT to create would be perfectly valid because for that server node the resource does not exist. – Justin Ohms – 2017-02-06T19:48:37.357

@JustinOhms I agree completely it's about separating concerns. I also agree there are edge cases for using PUT (one encountered recently by me involved a data import than needed the ability to re-run). The approach you have outlined above works because the server "instruct(s) clients on how to construct appropriate URIs", (Roy Fielding's words). However, it is not obvious to me why that is better than just using POST as intended. – Joshcodes – 2017-02-06T20:48:39.607

@Joshcodes The reason to use a PUT like this in a multi node setup is that that for the client to switch from PUT to POST the client would require knowledge about the state of the data on that node. It seems odd because we are often think of the server as being a single authority however in a distributed system with eventual consistency the client may actually have more information than any given server node at any point in time. In this case the client knows the resource exists, the node does not. (maybe a sync is needed) Plus POST would not be appropriate because the resource does exist. – Justin Ohms – 2017-02-06T21:28:20.793

1

Yes, if the resource already exists, use PUT. However, in nearly all cases, the resources should be created with POST and the client should not provide the URL. Roy Fielding agrees with this statement FWIW: http://roy.gbiv.com/untangled/2008/rest-apis-must-be-hypertext-driven

– Joshcodes – 2017-02-07T01:26:05.267

links for AtomPub doesn't work anymore – guillaume guerin – 2018-07-25T09:57:07.577

58

Both are used for data transmission between client to server, but there are subtle differences between them, which are:

Enter image description here

Analogy:

  • PUT i.e. take and put where it was.
  • POST as send mail in post office.

enter image description here

Premraj

Posted 2009-03-10T14:25:20.390

Reputation: 27 989

5So in summary: POST for inserts, PUT for updates – MobileMon – 2015-09-22T12:31:19.817

13@MobileMon No, REST methods are not CRUD. – jlr – 2016-01-08T19:06:38.070

I'd say PUT for UPSERTS – Hola Soy Edu Feliz Navidad – 2018-11-26T11:45:16.307

55

The decision of whether to use PUT or POST to create a resource on a server with an HTTP + REST API is based on who owns the URL structure. Having the client know, or participate in defining, the URL struct is an unnecessary coupling akin to the undesirable couplings that arose from SOA. Escaping types of couplings is the reason REST is so popular. Therefore, the proper method to use is POST. There are exceptions to this rule and they occur when the client wishes to retain control over the location structure of the resources it deploys. This is rare and likely means something else is wrong.

At this point some people will argue that if RESTful-URL's are used, the client does knows the URL of the resource and therefore a PUT is acceptable. After all, this is why canonical, normalized, Ruby on Rails, Django URLs are important, look at the Twitter API … blah blah blah. Those people need to understand there is no such thing as a Restful-URL and that Roy Fielding himself states that:

A REST API must not define fixed resource names or hierarchies (an obvious coupling of client and server). Servers must have the freedom to control their own namespace. Instead, allow servers to instruct clients on how to construct appropriate URIs, such as is done in HTML forms and URI templates, by defining those instructions within media types and link relations. [Failure here implies that clients are assuming a resource structure due to out-of band information, such as a domain-specific standard, which is the data-oriented equivalent to RPC's functional coupling].

http://roy.gbiv.com/untangled/2008/rest-apis-must-be-hypertext-driven

The idea of a RESTful-URL is actually a violation of REST as the server is in charge of the URL structure and should be free to decide how to use it to avoid coupling. If this confuses you read about the significance of self discovery on API design.

Using POST to create resources comes with a design consideration because POST is not idempotent. This means that repeating a POST several times does not guarantee the same behavior each time. This scares people into using PUT to create resources when they should not. They know it's wrong (POST is for CREATE) but they do it anyway because they don't know how to solve this problem. This concern is demonstrated in the following situation:

  1. The client POST a new resource to the server.
  2. The server processes the request and sends a response.
  3. The client never receives the response.
  4. The server is unaware the client has not received the response.
  5. The client does not have a URL for the resource (therefore PUT is not an option) and repeats the POST.
  6. POST is not idempotent and the server …

Step 6 is where people commonly get confused about what to do. However, there is no reason to create a kludge to solve this issue. Instead, HTTP can be used as specified in RFC 2616 and the server replies:

10.4.10 409 Conflict

The request could not be completed due to a conflict with the current state of the resource. This code is only allowed in situations where it is expected that the user might be able to resolve the conflict and resubmit the request. The response body SHOULD include enough

information for the user to recognize the source of the conflict. Ideally, the response entity would include enough information for the user or user agent to fix the problem; however, that might not be possible and is not required.

Conflicts are most likely to occur in response to a PUT request. For example, if versioning were being used and the entity being PUT included changes to a resource which conflict with those made by an earlier (third-party) request, the server might use the 409 response to indicate that it can’t complete the request. In this case, the response entity would likely contain a list of the differences between the two versions in a format defined by the response Content-Type.

Replying with a status code of 409 Conflict is the correct recourse because:

  • Performing a POST of data which has an ID which matches a resource already in the system is “a conflict with the current state of the resource.”
  • Since the important part is for the client to understand the server has the resource and to take appropriate action. This is a “situation(s) where it is expected that the user might be able to resolve the conflict and resubmit the request.”
  • A response which contains the URL of the resource with the conflicting ID and the appropriate preconditions for the resource would provide “enough information for the user or user agent to fix the problem” which is the ideal case per RFC 2616.

Update based on release of RFC 7231 to Replace 2616

RFC 7231 is designed to replace 2616 and in Section 4.3.3 describes the follow possible response for a POST

If the result of processing a POST would be equivalent to a representation of an existing resource, an origin server MAY redirect the user agent to that resource by sending a 303 (See Other) response with the existing resource's identifier in the Location field. This has the benefits of providing the user agent a resource identifier and transferring the representation via a method more amenable to shared caching, though at the cost of an extra request if the user agent does not already have the representation cached.

It now may be tempting to simply return a 303 in the event that a POST is repeated. However, the opposite is true. Returning a 303 would only make sense if multiple create requests (creating different resources) return the same content. An example would be a "thank you for submitting your request message" that the client need not re-download each time. RFC 7231 still maintains in section 4.2.2 that POST is not to be idempotent and continues to maintain that POST should be used for create.

For more information about this, read this article.

Joshcodes

Posted 2009-03-10T14:25:20.390

Reputation: 5 347

Would a 409 Conflict response be the appropriate code for something like trying to create a new account with a username that already exists? I've been using 409 for versioning conflicts specifically, but after reading your answer, I wonder if it shouldn't be used for any "duplicate" requests. – Eric B. – 2014-07-09T04:43:34.577

@EricB. Yes, in the situation you describe "due to a conflict with the current state of the resource" the operation fails. Additionally, it is reasonable to expect that the user can resolve the conflict and the message body only needs to inform the user that the username already exists. – Joshcodes – 2014-07-10T13:25:23.680

@Joshcodes can you say more about the conflict resolution process? In this case, if the username already exists is the client expected to prompt the end user for a different username? What if the client is actually trying to use POST to change the username? Should PUT requests still be used for updating parameters, while POST is used for creating objects whether it be one at a time or several? Thanks. – BFar – 2015-01-22T22:41:13.923

@BFar2 if the username already exists then the client should prompt the user. To change the username, assuming the username is part of an already created resource which needs modified, PUT would be used because you are correct, POST is used for create, always and PUT for updates. – Joshcodes – 2015-01-23T01:09:44.773

explaining things using short and effective language is also a desirable skill – Junchen Liu – 2015-08-24T16:27:49.173

@Joshcodes i'm seeking an answer to http://stackoverflow.com/questions/39057416/how-to-ignore-multiple-clicks-from-an-impatient-user. commenting now to point your attention to it.

– Roam – 2016-08-20T19:20:24.987

@Joshcodes i'm aware the work on http://stackoverflow.com/questions/39057416/how-to-ignore-multiple-clicks-from-an-impatient-user doesn't comply w/Restful architecture. yet works for our case as an exception.

– Roam – 2016-08-20T19:21:14.123

@Joshcodes Interesting. to clarify: Performing a POST of data which has an ID which matches a resource already in the system is a conflict" Isn't your prescription that a POST never includes an ID since the server decides the ID? – Iain – 2017-09-23T23:46:53.430

Iain, the client determines the ID. The server determines the URL. – Joshcodes – 2017-09-24T14:01:00.207

@Joshcodes How is the client to determine the ID? Generating a UUID? What about apps that just use the auto-incrementing table ID; something I see a lot. Is this just bad practice? – Zuko – 2018-02-25T01:41:56.987

@Zuko, In my opinion, auto-incrementing table IDs have no place in a distributed environment. UUID's are superior in every way except storage space. Ints for IDs are a holdover from when DB storage was a larger concern that it is today. – Joshcodes – 2018-03-05T18:14:56.953

51

I like this advice, from RFC 2616's definition of PUT:

The fundamental difference between the POST and PUT requests is reflected in the different meaning of the Request-URI. The URI in a POST request identifies the resource that will handle the enclosed entity. That resource might be a data-accepting process, a gateway to some other protocol, or a separate entity that accepts annotations. In contrast, the URI in a PUT request identifies the entity enclosed with the request -- the user agent knows what URI is intended and the server MUST NOT attempt to apply the request to some other resource.

This jibes with the other advice here, that PUT is best applied to resources that already have a name, and POST is good for creating a new object under an existing resource (and letting the server name it).

I interpret this, and the idempotency requirements on PUT, to mean that:

  • POST is good for creating new objects under a collection (and create does not need to be idempotent)
  • PUT is good for updating existing objects (and update needs to be idempotent)
  • POST can also be used for non-idempotent updates to existing objects (especially, changing part of an object without specifying the whole thing -- if you think about it, creating a new member of a collection is actually a special case of this kind of update, from the collection's perspective)
  • PUT can also be used for create if and only if you allow the client to name the resource. But since REST clients aren't supposed to make assumptions about URL structure, this is less in the intended spirit of things.

metamatt

Posted 2009-03-10T14:25:20.390

Reputation: 8 291

3"POST can also be used for non-idempotent updates to existing objects (especially, changing part of an object without specifying the whole thing" That's what PATCH is for – Snuggs – 2012-05-04T22:11:24.297

41

POST is like posting a letter to a mailbox or posting an email to an email queue. PUT is like when you put an object in a cubby hole or a place on a shelf (it has a known address).

With POST, you're posting to the address of the QUEUE or COLLECTION. With PUT, you're putting to the address of the ITEM.

PUT is idempotent. You can send the request 100 times and it will not matter. POST is not idempotent. If you send the request 100 times, you'll get 100 emails or 100 letters in your postal box.

A general rule: if you know the id or name of the item, use PUT. If you want the id or name of the item to be assigned by the receiving party, use POST.

POST versus PUT

Homer6

Posted 2009-03-10T14:25:20.390

Reputation: 9 387

1No, PUT implies that you know the URL. If you only know the ID then POST with that ID to get the URL. – Joshcodes – 2013-10-29T17:35:20.643

5The id is part of the URL, so yes, use PUT if you know the URL (which includes the id). – Homer6 – 2013-10-29T22:02:53.290

No, the URL is determined by the server and the ID is not necessarily part of the URL. Roy Fielding would tell you the same or you could just read his thesis.

– Joshcodes – 2013-10-29T23:06:18.100

@Joshcodes, is that assuming REST? In a RESTful architecture, the item id is most definitely part of the URL, as in: /people/123. I like this site for REST: http://microformats.org/wiki/rest/urls

– Beez – 2013-12-26T19:10:14.977

1

@Beez the mircoformats link suggests a good way for servers to structure their URLs but the server determines the URL. The client next-to-never does. See my answer or associated article if you don't understand this.

– Joshcodes – 2014-01-07T17:11:35.223

@Joshcodes, I'm not denying where a URL is determined. I'm saying that in a RESTful architecture (defined from the server on up), the ID is part of a URL. – Beez – 2014-01-07T20:21:44.987

@Beez if the server determines the URL, the URL should not be dictated by the client. Therefore, even if you know the ID, use POST not PUT. Whether the ID should be part of the URL is a different conversation. – Joshcodes – 2014-01-07T21:16:52.243

I think "General Rule" covers it generally having the ID or name in the URL. Great answer! – TamusJRoyce – 2015-05-11T04:48:13.657

@TamusJRoyce, Roy Fielding (the guy who created REST) would disagree with you: http://roy.gbiv.com/untangled/2008/rest-apis-must-be-hypertext-driven Also, while true that the ID will likely be provide by the client via the URL the client still does not know where in the URL to put the ID.

– Joshcodes – 2015-09-11T14:44:07.197

@beez and Homer6: Joshcodes is correct. Nothing about REST requires the ID to be in the URL, and a URL with a structure like /collection/:id does not imply that the website is RESTful. In fact, sites with non-HTML representations almost always aren't. – Nicholas Shanks – 2016-12-26T13:22:46.970

41

In short:

PUT is idempotent, where the resource state will be the same if the same operation is executed one time or multiple times.

POST is non-idempotent, where the resource state may become different if the operation is executed multiple times as compared to executing a single time.

Analogy with database query

PUT You can think of similar to "UPDATE STUDENT SET address = "abc" where id="123";

POST You can think of something like "INSERT INTO STUDENT(name, address) VALUES ("abc", "xyzzz");

Student Id is auto generated.

With PUT, if the same query is executed multiple times or one time, the STUDENT table state remains the same.

In case of POST, if the same query is executed multiple times then multiple Student records get created in the database and the database state changes on each execution of an "INSERT" query.

NOTE: PUT needs a resource location (already-resource) on which update needs to happen, whereas POST doesn't require that. Therefore intuitively POST is meant for creation of a new resource, whereas PUT is needed for updating the already existing resource.

Some may come up with that updates can be performed with POST. There is no hard rule which one to use for updates or which one to use for create. Again these are conventions, and intuitively I'm inclined with the above mentioned reasoning and follow it.

bharatj

Posted 2009-03-10T14:25:20.390

Reputation: 1 233

37

New answer (now that I understand REST better):

PUT is merely a statement of what content the service should, from now on, use to render representations of the resource identified by the client; POST is a statement of what content the service should, from now on, contain (possibly duplicated) but it's up to the server how to identify that content.

PUT x (if x identifies a resource): "Replace the content of the resource identified by x with my content."

PUT x (if x does not identify a resource): "Create a new resource containing my content and use x to identify it."

POST x: "Store my content and give me an identifier that I can use to identify a resource (old or new) containing said content (possibly mixed with other content). Said resource should be identical or subordinate to that which x identifies." "y's resource is subordinate to x's resource" is typically but not necessarily implemented by making y a subpath of x (e.g. x = /foo and y = /foo/bar) and modifying the representation(s) of x's resource to reflect the existence of a new resource, e.g. with a hyperlink to y's resource and some metadata. Only the latter is really essential to good design, as URLs are opaque in REST -- you're supposed to use hypermedia instead of client-side URL construction to traverse the service anyways.

In REST, there's no such thing as a resource containing "content". I refer as "content" to data that the service uses to render representations consistently. It typically consists of some related rows in a database or a file (e.g. an image file). It's up to the service to convert the user's content into something the service can use, e.g. converting a JSON payload into SQL statements.

Original answer (might be easier to read):

PUT /something (if /something already exists): "Take whatever you have at /something and replace it with what I give you."

PUT /something (if /something does not already exist): "Take what I give you and put it at /something."

POST /something: "Take what I give you and put it anywhere you want under /something as long as you give me its URL when you're done."

Jordan

Posted 2009-03-10T14:25:20.390

Reputation: 2 422

But how can you use PUT to create a new resource if it doesn't exist, while your ID generation method is on Auto Increment ? Usually ORM's does auto generate the ID for you, like the way you want it to be in a POST for example. Does it mean that if you want to implement PUT the right way you have to change your id auto generation ? This is awkward if the answer is yes. – Roni Axelrad – 2018-09-16T15:28:21.187

1@RoniAxelrad : PUT is like a database "INSERT OR UPDATE" statement where you are including the key in the statement, so only applicable where you can guarente no collisions. eg. your domain has a 'natural key' or you use a guid. POST is like inserting into a table with an auto incrementing key. You have to be told by the database what ID it got after it has been inserted. Note your "INSERT OR UPDATE" will replace any previous data if it existed. – Nigel Thorne – 2018-11-26T01:33:41.557

@NigelThorne Thanks for your answer. So if for example I'm trying to PUT a book id 10 with a URI: PUT books/10. If book id 10 does not exists, I should create a book with id 10 right? but I cannot control the creation ID numerator, because it's auto increment. what should I do in that situation ? – Roni Axelrad – 2018-11-27T20:50:43.740

34

Ruby on Rails 4.0 will use the 'PATCH' method instead of PUT to do partial updates.

RFC 5789 says about PATCH (since 1995):

A new method is necessary to improve interoperability and prevent errors. The PUT method is already defined to overwrite a resource with a complete new body, and cannot be reused to do partial changes. Otherwise, proxies and caches, and even clients and servers, may get confused as to the result of the operation. POST is already used but without broad interoperability (for one, there is no standard way to discover patch format support). PATCH was mentioned in earlier HTTP specifications, but not completely defined.

"Edge Rails: PATCH is the new primary HTTP method for updates" explains it.

germanlinux

Posted 2009-03-10T14:25:20.390

Reputation: 2 085

Really interesting, didn't see this blog post until now! Thanks for the link! – Nathan Kleyn – 2012-02-27T21:07:34.257

31

Short Answer:

Simple rule of thumb: Use POST to create, use PUT to update.

Long Answer:

POST:

  • POST is used to send data to server.
  • Useful when the resource's URL is unknown

PUT:

  • PUT is used to transfer state to the server
  • Useful when a resource's URL is known

Longer Answer:

To understand it we need to question why PUT was required, what were the problems PUT was trying to solve that POST couldn't.

From a REST architecture's point of view there is none that matters. We could have lived without PUT as well. But from a client developer's point of view it made his/her life a lot simpler.

Prior to PUT, clients couldn't directly know the URL that the server generated or if all it had generated any or whether the data to be sent to the server is already updated or not. PUT relieved the developer of all these headaches. PUT is idempotent, PUT handles race conditions, and PUT lets the client choose the URL.

ishandutta2007

Posted 2009-03-10T14:25:20.390

Reputation: 4 175

26

At the risk of restating what has already been said, it seems important to remember that PUT implies that the client controls what the URL is going to end up being, when creating a resource. So part of the choice between PUT and POST is going to be about how much you can trust the client to provide correct, normalized URL that are coherent with whatever your URL scheme is.

When you can't fully trust the client to do the right thing, it would be more appropriate to use POST to create a new item and then send the URL back to the client in the response.

skillet-thief

Posted 2009-03-10T14:25:20.390

Reputation: 459

2I'm a bit late to this - but someone saying something similar on another website got it to click for me. If you're creating a resource and using an auto-incremented ID as it's "identifier" instead of a user assigned name, it should be a POST. – Ixmatus – 2012-02-03T18:51:40.880

1This isn't quite right - PUT can still create a resource by referring to it with a non-canonical name, as long as in the response, the server returns a Location header that does contain the canonical resource name. – Ether – 2012-10-19T16:08:58.370

1@Joshcodes don't forget that you can have many URIs referencing the same underlying resource. So what Ether said is sound advice, the client can PUT to a URL (that might be more semantic, like PUT /X-files/series/4/episodes/max) and the server respond with a URI that provides a short canonical unique link to that new resource (ie /X-Ffiles/episodes/91) – thecoshman – 2015-06-08T08:02:33.380

@thecoshman the issue is the concern for the URL structure does not belong to the client. Reading about self-discovery (also part of REST) may help make this clear. – Joshcodes – 2015-06-08T17:50:32.890

@Joshcodes then by that logic, a client should never use PUT to create as they shouldn't be concerned with with providing the URL. Well... unless the server provided a URL to PUT to if the client wants to put to it... something like "PUT /comments/new" and the server might respond "204 /comments/234532" but that seems a bit RPC to me, the client should just POST to /comments... – thecoshman – 2015-06-09T16:18:27.370

@thecoshman yes, the client really should never use PUT. What's RPC about that? – Joshcodes – 2015-06-10T17:11:08.833

@thecoshman: no, you can't have multiple URLs pointing to one resource. Every unique URI is a unique resource, and every resource has one and only one URI. – Nicholas Shanks – 2016-12-26T13:38:45.067

@NicholasShanks not really. Consider a resource that represents a school student, you could access /student/123 but you might also get to that same student via /class/abc/student/123, That is perfectly valid. There is the concept of the canonical URI though, which in this case we could say the former is. The U is for Uniform, not Unique. – thecoshman – 2017-01-09T13:41:13.943

@thecoshman What you would then have is two identical resources that just happen to change every time the other one does. A link from one to the other with a canonical relation would definitely help though. Even if you supplied a Content-Location header with one, pointing to the path of the other, that would not unify the underlying resources represented by each URL. Consider that a representation is not a resource, and two identical representations do not make the same resource (e.g. downloads/v1.0.0/ and downloads/latest-version/) – Nicholas Shanks – 2017-01-09T15:34:09.520

@NicholasShanks I think this answer provides a good explanation that I agree with but also considers your point of view. I'd also say that it is probably a more relevant place for this discussion.

– thecoshman – 2017-01-09T16:48:40.917

20

The most important consideration is reliability. If a POST message gets lost the state of the system is undefined. Automatic recovery is impossible. For PUT messages, the state is undefined only until the first successful retry.

For instance, it may not be a good idea to create credit card transactions with POST.

If you happen to have auto generated URI's on your resource you can still use PUT by passing a generated URI (pointing to an empty resource) to the client.

Some other considerations:

  • POST invalidates cached copies of the entire containing resource (better consistency)
  • PUT responses are not cacheable while POST ones are (Require Content-Location and expiration)
  • PUT is less supported by e.g. Java ME, older browsers, firewalls

Hans Malherbe

Posted 2009-03-10T14:25:20.390

Reputation: 2 420

This is incorrect. For POST, the state is also undefined only until the first successful retry. Then, either the server accepts the POST (message never arrived), throws a 409 conflict for a duplicate ID (message arrived, response was lost), or any other valid response. – Joshcodes – 2014-04-24T12:13:04.630

In general a useragent would not able to safely retry the POST operation since the POST operation gives no that guarantee that two operations would have the same effect as one. The term "ID" has nothing to do with HTTP. The URI identifies the resource. – Hans Malherbe – 2014-07-25T05:48:18.827

A useragent can "safely" retry a POST operation as many times as it wants. It will just receive a duplicate ID error (assuming the resource has an ID) or a duplicate data error (assuming that's an issue and the resource does not have IDs). – Joshcodes – 2014-07-27T02:10:02.007

Bangs head against wall. HTTP has no solution to the problem of reliability, and this is not well understood, not much discussed, and simply not catered for in the vast majority of web applications. @Joshcodes I have an answer to this question. I essentially agree with Hans. There's a problem. – bbsimonbb – 2018-06-13T08:21:20.427

@bbsimonbb, HTTP has a robust and well documented set of error responses. My answer to this question (https://stackoverflow.com/questions/630453/put-vs-post-in-rest/9197466#19670755) covers how to use http according to specification to achieve consistency.

– Joshcodes – 2018-06-19T12:50:19.480

invalidates cached copies of the entire containing resource any reference for that? Also it's never mandatory for a browser to follow the cache rules set. – Honey – 2018-11-26T16:50:55.653

19

In a very simple way I'm taking the example of the Facebook timeline.

Case 1: When you post something on your timeline, it's a fresh new entry. So in this case they use the POST method because the POST method is non-idempotent.

Case 2: If your friend comment on your post the first time, that also will create a new entry in the database so the POST method used.

Case 3: If your friend edits his comment, in this case, they had a comment id, so they will update an existing comment instead of creating a new entry in the database. Therefore for this type of operation use the PUT method because it is idempotent.*

In a single line, use POST to add a new entry in the database and PUT to update something in the database.

UniCoder

Posted 2009-03-10T14:25:20.390

Reputation: 1 076

14

There seems to always be some confusion as to when to use the HTTP POST versus the HTTP PUT method for REST services. Most developers will try to associate CRUD operations directly to HTTP methods. I will argue that this is not correct and one can not simply associate the CRUD concepts to the HTTP methods. That is:

Create => HTTP PUT
Retrieve => HTTP GET
Update => HTTP POST
Delete => HTTP DELETE

It is true that the R(etrieve) and D(elete) of the CRUD operations can be mapped directly to the HTTP methods GET and DELETE respectively. However, the confusion lies in the C(reate) and U(update) operations. In some cases, one can use the PUT for a create while in other cases a POST will be required. The ambiguity lies in the definition of an HTTP PUT method versus an HTTP POST method.

According to the HTTP 1.1 specifications the GET, HEAD, DELETE, and PUT methods must be idempotent, and the POST method is not idempotent. That is to say that an operation is idempotent if it can be performed on a resource once or many times and always return the same state of that resource. Whereas a non idempotent operation can return a modified state of the resource from one request to another. Hence, in a non idempotent operation, there is no guarantee that one will receive the same state of a resource.

Based on the above idempotent definition, my take on using the HTTP PUT method versus using the HTTP POST method for REST services is: Use the HTTP PUT method when:

The client includes all aspect of the resource including the unique identifier to uniquely identify the resource. Example: creating a new employee.
The client provides all the information for a resource to be able to modify that resource.This implies that the server side does not update any aspect of the resource (such as an update date).

In both cases, these operations can be performed multiple times with the same results. That is the resource will not be changed by requesting the operation more than once. Hence, a true idempotent operation. Use the HTTP POST method when:

The server will provide some information concerning the newly created resource. For example, take a logging system. A new entry in the log will most likely have a numbering scheme which is determined on the server side. Upon creating a new log entry, the new sequence number will be determined by the server and not by the client.
On a modification of a resource, the server will provide such information as a resource state or an update date. Again in this case not all information was provided by the client and the resource will be changing from one modification request to the next. Hence a non idempotent operation.

Conclusion

Do not directly correlate and map CRUD operations to HTTP methods for REST services. The use of an HTTP PUT method versus an HTTP POST method should be based on the idempotent aspect of that operation. That is, if the operation is idempotent, then use the HTTP PUT method. If the operation is non idempotent, then use the HTTP POST method.

Burhan

Posted 2009-03-10T14:25:20.390

Reputation: 193

1Update => HTTP POST : POST is not for updating – Premraj – 2016-01-30T00:57:59.177

12

the origin server can create the resource with that URI

So you use POST and probably, but not necessary PUT for resource creation. You don't have to support both. For me POST is perfectly enough. So it is a design decision.

As your quote mentioned, you use PUT for creation of there is no resource assigned to an IRI, and you want to create a resource anyway. For example, PUT /users/123/password usually replaces the old password with a new one, but you can use it to create a password if it does not exist already (for example, by freshly registered users or by restoring banned users).

inf3rno

Posted 2009-03-10T14:25:20.390

Reputation: 14 217

I think you've managed to provide one of the few good examples of how to use PUT, well done. – thecoshman – 2015-06-08T08:13:00.773

12

Readers new to this topic will be struck by the endless discussion about what you should do, and the relative absence of lessons from experience. The fact that REST is "preferred" over SOAP is, I suppose, a high-level learning from experience, but goodness we must have progressed from there? It's 2016. Roy's dissertation was in 2000. What have we developed? Was it fun? Was it easy to integrate with? To support? Will it handle the rise of smartphones and flaky mobile connections?

According to ME, real-life networks are unreliable. Requests timeout. Connections are reset. Networks go down for hours or days at a time. Trains go into tunnels with mobile users aboard. For any given request (as occasionally acknowledged in all this discussion) the request can fall in the water on its way, or the response can fall in the water on its way back. In these conditions, issuing PUT, POST and DELETE requests directly against substantive resources has always struck me as a little brutal and naive.

HTTP does nothing to ensure reliable completion of the request-response, and that's just fine because this is properly the job of network-aware applications. Developing such an application, you can jump through hoops to use PUT instead of POST, then more hoops to give a certain kind of error on the server if you detect duplicate requests. Back at the client, you then have to jump through hoops to interpret these errors, refetch, revalidate and repost.

Or you can do this: consider your unsafe requests as ephemeral single-user resources (let's call them actions). Clients request a new "action" on a substantive resource with an empty POST to the resource. POST will be used only for this. Once safely in possession of the URI of the freshly minted action, the client PUTs the unsafe request to the action URI, not the target resource. Resolving the action and updating the "real" resource is properly the job of your API, and is here decoupled from the unreliable network.

The server does the business, returns the response and stores it against the agreed action URI. If anything goes wrong, the client repeats the request (natural behaviour!), and if the server has already seen it, it repeats the stored response and does nothing else.

You will quickly spot the similarity with promises: we create and return the placeholder for the result before doing anything. Also like a promise, an action can succeed or fail one time, but its result can be fetched repeatedly.

Best of all, we give sending and receiving applications a chance to link the uniquely identified action to uniqueness in their respective environments. And we can start to demand, and enforce!, responsible behaviour from clients: repeat your requests as much as you like, but don't go generating a new action until you're in possession of a definitive result from the existing one.

As such, numerous thorny problems go away. Repeated insert requests won't create duplicates, and we don't create the real resource until we're in possession of the data. (database columns can stay not-nullable). Repeated update requests won't hit incompatible states and won't overwrite subsequent changes. Clients can (re)fetch and seamlessy process the original confirmation for whatever reason (client crashed, response went missing, etc.).

Successive delete requests can see and process the original confirmation, without hitting a 404 error. If things take longer than expected, we can respond provisionally, and we have a place where the client can check back for the definitive result. The nicest part of this pattern is its Kung-Fu (Panda) property. We take a weakness, the propensity for clients to repeat a request any time they don't understand the response, and turn it into a strength :-)

Before telling me this is not RESTful, please consider the numerous ways in which REST principles are respected. Clients don't construct URLs. The API stays discoverable, albeit with a little change in semantics. HTTP verbs are used appropriately. If you think this is a huge change to implement, I can tell you from experience that it's not.

If you think you'll have huge amounts of data to store, let's talk volumes: a typical update confirmation is a fraction of a kilobyte. HTTP currently gives you a minute or two to respond definitively. Even if you only store actions for a week, clients have ample chance to catch up. If you have very high volumes, you may want a dedicated acid-compliant key value store, or an in-memory solution.

bbsimonbb

Posted 2009-03-10T14:25:20.390

Reputation: 8 696

10

I'm going to land with the following:

PUT refers to a resource, identified by the URI. In this case, you are updating it. It is the part of the three verbs referring to resources -- delete and get being the other two.

POST is basically a free form message, with its meaning being defined 'out of band'. If the message can be interpreted as adding a resource to a directory, that would be OK, but basically you need to understand the message you are sending (posting) to know what will happen with the resource.


Because PUT and GET and DELETE refer to a resource, they are also by definition idempotent.

POST can perform the other three functions, but then the semantics of the request will be lost on the intermediaries such as caches and proxies. This also applies to providing security on the resource, since a post's URI doesn't necessarily indicate the resource it is applying to (it can though).

A PUT doesn't need to be a create; the service could error if the resource isn't already created, but otherwise update it. Or vice versa -- it may create the resource, but not allow updates. The only thing required about PUT is that it points to a specific resource, and its payload is the representation of that resource. A successful PUT means (barring interference) that a GET would retrieve the same resource.


Edit: One more thing -- a PUT can create, but if it does then the ID has to be a natural ID -- AKA an email address. That way when you PUT twice, the second put is an update of the first. This makes it idempotent.

If the ID is generated (a new employee ID, for example), then the second PUT with the same URL would create a new record, which violates the idempotent rule. In this case the verb would be POST, and the message (not resource) would be to create a resource using the values defined in this message.

Gerard ONeill

Posted 2009-03-10T14:25:20.390

Reputation: 2 286

9

The semantics are supposed be different, in that "PUT", like "GET" is supposed to be idempotent -- meaning, you can the same exact PUT request multiple times and the result will be as if you executed it only once.

I will describe the conventions which I think are most widely used and are most useful:

When you PUT a resource at a particular URL what happens is that it should get saved at that URL, or something along those lines.

When you POST to a resource at a particular URL, often you are posting a related piece of information to that URL. This implies that the resource at the URL already exists.

For example, when you want to create a new stream, you can PUT it to some URL. But when you want to POST a message to an existing stream, you POST to its URL.

As for modifying the properties of the stream, you can do that with either PUT or POST. Basically, only use "PUT" when the operation is idempotent - otherwise use POST.

Note, however, that not all modern browsers support HTTP verbs other than GET or POST.

Gregory Magarshak

Posted 2009-03-10T14:25:20.390

Reputation: 668

What you describe POST as is actually how PATCH should behave. POST is supposed to mean something more akin to "append" as in "post to mailing list". – Alexander Torstling – 2014-11-28T15:57:25.600

7

While there is probably an agnostic way to describe these, it does seem to be conflicting with various statements from answers to websites.

Let's be very clear and direct here. If you are a .NET developer working with Web API, the facts are (from the Microsoft API documentation), http://www.asp.net/web-api/overview/creating-web-apis/creating-a-web-api-that-supports-crud-operations:

1. PUT = UPDATE (/api/products/id)
2. MCSD Exams 2014 -  UPDATE = PUT, there are **NO** multiple answers for that question period.

Sure you "can" use "POST" to update, but just follow the conventions laid out for you with your given framework. In my case it is .NET / Web API, so PUT is for UPDATE there is no debate.

I hope this helps any Microsoft developers that read all comments with Amazon and Sun/Java website links.

Tom Stickel

Posted 2009-03-10T14:25:20.390

Reputation: 12 064

7

Most of the time, you will use them like this:

  • POST a resource into a collection
  • PUT a resource identified by collection/:id

For example:

  • POST /items
  • PUT /items/1234

In both cases, the request body contains the data for the resource to be created or updated. It should be obvious from the route names that POST is not idempotent (if you call it 3 times it will create 3 objects), but PUT is idempotent (if you call it 3 times the result is the same). PUT is often used for "upsert" operation (create or update), but you can always return a 404 error if you only want to use it to modify.

Note that POST "creates" a new element in the collection, and PUT "replaces" an element at a given URL, but it is a very common practice to use PUT for partial modifications, that is, use it only to update existing resources and only modify the included fields in the body (ignoring the other fields). This is technically incorrect, if you want to be REST-purist, PUT should replace the whole resource and you should use PATCH for the partial update. I personally don't care much as far as the behavior is clear and consistent across all your API endpoints.

Remember, REST is a set of conventions and guidelines to keep your API simple. If you end up with a complicated work-around just to check the "RESTfull" box then you are defeating the purpose ;)

tothemario

Posted 2009-03-10T14:25:20.390

Reputation: 3 381

6

If you are familiar with database operations, there are

  1. Select
  2. Insert
  3. Update
  4. Delete
  5. Merge (Update if already existing, else insert)

I use PUT for Merge and update like operations and use POST for Insertions.

Rajan

Posted 2009-03-10T14:25:20.390

Reputation: 950

5

Here's a simple rule:

PUT to a URL should be used to update or create the resource that can be located at that URL.

POST to a URL should be used to update or create a resource which is located at some other ("subordinate") URL, or is not locatable via HTTP.

Adam Griffiths

Posted 2009-03-10T14:25:20.390

Reputation: 1 141

1PUT is not for update, it is for replace, note that to create you are replacing nothing with something. POST is absolutely not for update in any shape of form. – thecoshman – 2015-06-08T08:10:32.277

1Does the http spec say that? Or are you basing your comment on something else? – Adam Griffiths – 2016-07-10T20:41:57.210

It's just common sense, how you update something when you don't know what it is you are updating? POST is for creating a new resource. – thecoshman – 2016-07-27T09:23:42.467

2thecoshman -- you are abusing semantics here -- a replace can be an update if it is the same resource with a few differences. A replace is only valid for put if replace is used to change the same resource. Replacing with a new and different resource is invalid (remove old and add new?), especially if the 'new' resource doesn't have a natural ID. POST, OTOH, is something that can create, update, replace, and delete -- using post depends on whether or not there is a message to interpret, such as 'apply the discount', which may or may not change the resource depending on logic. – Gerard ONeill – 2016-12-28T16:54:04.530

As for your second comment -- how about you 'get' the resource, modify the fields you need to, and then put it back? Or how about if the resource comes from a different source but uses a natural ID (the external ID) -- put would naturally update the resource at the URL when the original data changed. – Gerard ONeill – 2016-12-28T16:56:26.087

5

In practice, POST works well for creating resources. The URL of the newly created resource should be returned in the Location response header. PUT should be used for updating a resource completely. Please understand that these are the best practices when designing a RESTful API. HTTP specification as such does not restrict using PUT/POST with a few restrictions for creating/updating resources. Take a look at http://techoctave.com/c7/posts/71-twitter-rest-api-dissected that summarizes the best practices.

java_geek

Posted 2009-03-10T14:25:20.390

Reputation: 6 834

For the most part, from reading through all this noise, you seem on the ball. I would say though, we should refer to PUT as the replace method, rather than the create/update. I think it better describes in one what it does. – thecoshman – 2015-06-08T08:15:20.667

4

In addition to differences suggested by others, I want to add one more.

In POST method you can send body params in form-data

In PUT method you have to send body params in x-www-form-urlencoded

Header Content-Type:application/x-www-form-urlencoded

According to this, you cannot send files or multipart data in the PUT method

EDIT

The content type "application/x-www-form-urlencoded" is inefficient for sending large quantities of binary data or text containing non-ASCII characters. The content type "multipart/form-data" should be used for submitting forms that contain files, non-ASCII data, and binary data.

Which means if you have to submit

files, non-ASCII data, and binary data

you should use POST method

Rohit Dhiman

Posted 2009-03-10T14:25:20.390

Reputation: 1 768

3

POST: Use it for creating new resources. It's like INSERT (SQL statement) with an auto-incremented ID. In the response part it contains a new generated Id.

POST is also used for updating a record.

PUT: Use it for creating a new resource, but here I know the identity key. It's like INSERT (SQL statement) where I know in advance the identity key. In the response part it sends nothing.

PUT is also used for updating a resource

sushil pandey

Posted 2009-03-10T14:25:20.390

Reputation: 619

6PUT is not for update, it is for replace, note that to create you are replacing nothing with something. POST is absolutely not for update in any shape of form. – thecoshman – 2015-06-08T08:11:59.233

Its good differences are given here https://restfulapi.net/rest-put-vs-post/

– Shivendra Prakash Shukla – 2018-03-22T09:57:51.717

2

So, which one should be used to create a resource? Or one needs to support both?

You should use PATCH. You PATCH the list of questions like

PATCH /questions HTTP/1.1

with a list containing your to be created object like

[
    {
        "title": "I said semantics!",
        "content": "Is this serious?",
        "answer": "Not really"
    }
]

It's a PATCH request as

  • you modify the existing list of resources without providing the whole new content
  • you change the state of your new question from non-existing to existing without providing all the data (the server will most probably add an id).

A great advantage of this method is that you can create multiple entities using a single request, simply by providing them all in the list.

This is something PUT obviously can't. You could use POST for creating multiple entities as it's the kitchen sink of HTTP and can do basically everything.

A disadvantage is that probably nobody uses PATCH this way. I'm afraid, I just invented it, but I hope, I provided a good argumentation.

You could use CREATE instead, as custom HTTP verbs are allowed, it's just that they mayn't work with some tools.

Concerning semantics, CREATE is IMHO the only right choice, everything else is a square peg in a round hole. Unfortunately, all we have are round holes.

maaartinus

Posted 2009-03-10T14:25:20.390

Reputation: 26 621