What is the difference between POST and PUT?

POST and PUT are HTTP methods used to send data to a server, but with different semantics:

• POST is used to create a new resource. POST requests are usually not idempotent, meaning that repeated requests can create multiple resources.
• PUT is used to create or completely update a resource at a known URI. PUT is idempotent — repeated requests with the same data will not change the result.

Example:

• POST /users — creates a new user, with the server generating the ID.
• PUT /users/123 — creates or updates the user with ID 123.

Thus, POST is for creation with server-managed identifiers, while PUT is for creating or replacing a resource at a specific address.