HTTP 304 Not Modified
The resource has not been modified since the last request.
3xx Redirection
304
Not Modified
Description
The 304 Not Modified status code indicates that a conditional GET or HEAD request has been received and would have resulted in a 200 OK response if it were not for the fact that the condition evaluated to false. In other words, there is no need for the server to transfer a representation of the target resource because the request indicates that the client, which made the request conditional, already has a valid representation. The server is therefore redirecting the client to make use of that stored representation as if it were the payload of a 200 OK response. The 304 response must not contain a message-body and is always terminated by the first empty line after the header fields.
When Is It Used?
Used for cache validation. When a client sends a conditional request with If-Modified-Since or If-None-Match headers, the server returns 304 if the resource has not changed, saving bandwidth by not resending the full response body.
Example Response
HTTP/1.1 304 Not Modified
ETag: "33a64df5"
Cache-Control: max-age=3600