The PATCH
applies partial modifications to a resource.
PATCH
is somewhat analogous to the "update" concept found in CRUD (in general, HTTP is different than CRUD, and the two should not be confused).
A PATCH
request is considered a set of instructions on how to modify a resource. Contrast this with PUT
; which is a complete representation of a resource.
A PATCH
is not necessarily idempotent, although it can be. Contrast this with PUT
; which is always idempotent. The word "idempotent" means that any number of repeated, identical requests will leave the resource in the same state. For example if an auto-incrementing counter field is an integral part of the resource, then a PUT
will naturally overwrite it (since it overwrites everything), but not necessarily so for PATCH
.
PATCH
(like POST
) may have side-effects on other resources.
To find out whether a server supports PATCH
, a server can advertise its support by adding it to the list in the Allow
or Access-Control-Allow-Methods
(for CORS) response headers.
Another (implicit) indication that PATCH
is allowed, is the presence of the Accept-Patch
header, which specifies the patch document formats accepted by the server.
Request has body | Yes |
---|---|
Successful response has body | Yes |
Safe | No |
Idempotent | No |
Cacheable | No |
Allowed in HTML forms | No |