Which HTTP methods ensure idempotency on repeated requests?

HTTP methods' idempotency means that repeating the same request will not change the server's state after the first call.

The main idempotent methods include:

• GET — retrieves data, does not change the state.
• PUT — updates a resource, repeated requests with the same data will not change the result.
• DELETE — deletes a resource, repeated calls will delete the resource once, subsequent calls will not change the state.
• HEAD — similar to GET but without the response body, is idempotent.
• OPTIONS — requests available methods, does not change the state.

The POST method is not idempotent, as repeated requests can create new resources or change the server's state.