The Difference between the HTTP methods PUT and POST

It seems that almost everyone is using RESTful APIs everywhere. A very common question that comes up is which of the two HTTP methods PUT and POST should be used in a particular situation. In this post, I will describe my understanding of the difference between the two methods.

The PUT method

  • It can be used to create or update resources.
  • It is idempotent. This means that multiple invocations of this HTTP method will produce the same result. In other words, there are no side effects.
  • It needs an exact URI location. This can be a problem if the server is responsible for generating unique resource identifiers.
PUT /products/123
{ }

The POST method

  • It can be use to only create resources.
  • It is not idempotent.
  • It does not expect an URI to contain a resource identifier.
  • The server should respond with a location header element.
  • Location: /products/456
  • Returning the newly created resource object is optional.

Of course, all this looks great in theory. However, I have run into scenarios that did not fit either method perfectly. And sometimes, technical considerations have forced me to go against these guidelines. But in the majority of the cases, I have found that the above rules work well for me.

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