Which HTTP method is commonly used to update existing resources?

The HTTP method commonly used to update existing resources is PUT. This method is specifically designed for this purpose as it allows clients to send data to the server that will replace the current representation of the resource identified by the URI. When a PUT request is made, it typically contains the full representation of the resource, ensuring that the server updates it accordingly.

PUT is idempotent, meaning that making the same request multiple times will not change the result beyond the initial application, which is a key characteristic for operations that modify existing resources. This makes it an appropriate choice for updates, as the result remains consistent regardless of how many times the method is called.

In contrast, the other methods serve different purposes. For instance, GET is used to retrieve resources without making any modifications, POST is usually employed to create new resources rather than updating existing ones, and DELETE is specifically used to remove resources from the server. Understanding these distinctions helps clarify why PUT is the correct choice for updating resources.