Conditional · Request header
If-None-Match
Send the resource only if its ETag has changed.
What is If-None-Match?
If-None-Match asks the server to return the resource only if its current ETag differs from the one the client cached. Otherwise the server responds with 304 Not Modified and no body.
Typical usage
Sent automatically by browsers when re-requesting a cached resource with an ETag.
Examples
If-None-Match: "33a64df5-e4d42a"Specification
RFC 9110 §13.1.2
Frequently asked questions
What is the If-None-Match HTTP header?
If-None-Match asks the server to return the resource only if its current ETag differs from the one the client cached. Otherwise the server responds with 304 Not Modified and no body.
Is If-None-Match a request or response header?
If-None-Match is a request header — the client sends it to the server. Sent automatically by browsers when re-requesting a cached resource with an ETag.
What does a If-None-Match header look like?
A typical If-None-Match header looks like: If-None-Match: "33a64df5-e4d42a".