Does HTTP PATCH method restrict updates to only one field at a time? Can I modify more than one field in a PATCH request? Can PATCH be used for modifying all the fields?
Does HTTP
PATCHmethod restrict updates to only one field at a time?
No.
Can I modify more than one field in a
PATCHrequest?
Of course.
Can
PATCHbe used for modifying all the fields?
Yes. But you may consider PUT for that purpose. And, depending on your needs, you may consider supporting PATCH along with PUT in your API.
The PATCH method definition doesn’t enforce any format for the request payload apart from mentioning that the request payload should contain a set of instructions describing how the resource will be modified and that set of instructions is identified by a media type (which defines how the PATCH should be applied by the server).
From the RFC 5789:
The
PATCHmethod requests that a set of changes described in the request entity be applied to the resource identified by the Request-URI. The set of changes is represented in a format called a “patch document” identified by a media type. […]
Some suitable formats for describing such set of changes are:
application/json-patch+json)application/merge-patch+json)I've added more details about each of these formats in this answer along with a comparison with PUT. So I strongly encourage you to have a look.