What is the difference between POST and PUT in HTTP?

In the HTTP protocol, POST and PUT are both methods used to submit data, but they have some key differences:

1. Idempotency:

   • PUT is idempotent, meaning that performing the same PUT operation multiple times will yield the same result. In other words, repeating the same PUT request should always produce identical outcomes.
   • POST is not idempotent. Each invocation of POST may result in the creation of new resources on the server or trigger different operations, even when the request is identical.

2. Purpose:

   • PUT is typically used to update or replace an existing resource. If the specified resource does not exist, PUT may create a new resource.
   • POST is typically used to create new resources. Additionally, POST can be used to trigger operations that are not solely for creating resources.

3. Meaning of URL:

   • When sending a PUT request, you typically include the complete URL of the resource. For example, to update specific user information, you might send a PUT request to /users/123, where 123 is the user ID.
   • POST requests are usually sent to a URL that handles a collection of resources. For instance, you can send a POST request to /users to create a new user, and the server generates the specific user ID during creation.

Example:

Assume we have a blog platform where we need to handle users' blog articles.

• To update an existing article, we can use PUT. For example, if the article ID is 456, we can send a PUT request to /articles/456. This request updates the article with ID 456, or if the article does not exist, it may create a new one (the behavior depends on the server implementation).

• To create a new article, we use POST and send it to /articles. After receiving the POST request, the server creates a new article and assigns a new ID, then returns details of the new resource, including its ID.

In summary, PUT is primarily used for update operations, while POST is primarily used for creating new resources.