Recap: HTTP Methods and Their Guarantees

The method is the part of an API call that everything between client and server understands.

• An API call is an HTTP request: method, path, headers, an optional body, and a status code back.
• GET reads, POST asks the server to process, PUT replaces, PATCH changes part, DELETE removes.
• Safe methods ask for no change; idempotent methods leave the same state however often they are sent.
• GET vs POST is chosen by what the operation does, not the size of its input.
• PUT sends the whole resource; PATCH sends changes and is idempotent only when they set values.
• QUERY is a safe, idempotent read with a body.
• A GET must never change data, because software sends GETs without asking anyone.