Idempotence means repeated operations yield the same result. Which statement correctly identifies idempotent HTTP methods?

• A. POST, GET, and PATCH are idempotent; PUT is not.
• B. All HTTP methods are idempotent.
• C. GET, PUT, and DELETE are idempotent; POST is not.
• D. Only GET is idempotent.

Answer: (C)

Idempotence in HTTP means sending the same request multiple times has the same effect as sending it once. The methods that are idempotent are GET, PUT, and DELETE. GET is idempotent because it simply retrieves data without changing anything on the server, so repeated requests don’t alter state. PUT is idempotent because sending the same payload to replace a resource results in the same final state each time. DELETE is idempotent because once the resource is removed, subsequent delete attempts don’t change the outcome (the resource remains gone, typically returning not found). POST, on the other hand, usually creates a new resource or triggers actions with side effects, so repeating it can lead to multiple resources or additional changes. This is why the statement that GET, PUT, and DELETE are idempotent while POST is not reflects standard HTTP behavior.