The 204 (No Content) status code indicates that the server has
successfully fulfilled the request and that there is no additional
content to send in the response payload body. Metadata in the
response header fields refer to the target resource and its selected
representation after the requested action was applied.
For example, if a 204 status code is received in response to a PUT
request and the response contains an ETag header field, then the PUT
was successful and the ETag field-value contains the entity-tag for
the new representation of that target resource.
The 204 response allows a server to indicate that the action has been
successfully applied to the target resource, while implying that the
user agent does not need to traverse away from its current “document
view” (if any). The server assumes that the user agent will provide
some indication of the success to its user, in accord with its own
interface, and apply any new or updated metadata in the response to
its active representation.
For example, a 204 status code is commonly used with document editing
interfaces corresponding to a “save” action, such that the document
being saved remains available to the user for editing. It is also
frequently used with interfaces that expect automated data transfers
to be prevalent, such as within distributed version control systems.
A 204 response is terminated by the first empty line after the header
fields because it cannot contain a message body.
A 204 response is cacheable by default; i.e., unless otherwise
indicated by the method definition or explicit cache controls (see