Which HTTP methods do not preserve idempotency when executed repeatedly?

HTTP methods that do not preserve idempotency when executed repeatedly are primarily POST.

• POST is used for creating resources or performing operations that can change the server's state and lead to different results upon repeated requests (for example, creating multiple records).

In contrast, methods like GET, PUT, DELETE, HEAD, OPTIONS, TRACE are considered idempotent, meaning that executing the same request multiple times will not change the server's state beyond the first call.

Example:

POST /orders HTTP/1.1
Host: example.com
Content-Type: application/json

{"item": "book", "quantity": 1}

Repeating the POST may create multiple orders, so it is not idempotent.