HTTP request method

An HTTP request method identifies the operation requested for an HTTP request's target. The target and method have separate roles: the same resource can be read, replaced or processed according to the chosen method and its defined semantics. Method tokens are case-sensitive.^[ref]

For example, an invented /color resource uses GET to retrieve its current color and PUT to replace that color with the supplied value. One PUT storing blue and two identical such operations leave the same intended color. A different /log resource is stipulated to append each POST value: two appends of x then produce two entries. The append behavior belongs to this example application; it is not a universal definition of every POST.

HTTP idempotence concerns repeated intended effects, not identical response messages. A repeated replacement can leave the same state while returning a different HTTP status code because the resource already exists. An HTTP safe method requests essentially read-only semantics; incidental activities such as logging do not make every safe request a request to change the resource.^[ref]

Cacheability is another property, governed by method and response rules rather than by idempotence alone. Interpret the HTTP request method, HTTP header fields and HTTP response together before deciding what a repeated or cached exchange means.^[ref]