Constant VARY
pub const VARY: HeaderName;Available on crate feature
http only.Expand description
Determines how to match future requests with cached responses.
The vary HTTP response header determines how to match future request
headers to decide whether a cached response can be used rather than
requesting a fresh one from the origin server. It is used by the server
to indicate which headers it used when selecting a representation of a
resource in a content negotiation algorithm.
The vary header should be set on a 304 Not Modified response exactly
like it would have been set on an equivalent 200 OK response.