Vary header

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since ⁨July 2015⁩.

The HTTPVaryresponse header describes the parts of the request message (aside from the method and URL) that influenced the content of the response it occurs in.Including aVary header ensures that responses are separately cached based on the headers listed in theVary field.Most often, this is used to create a cache key whencontent negotiation is in use.

The sameVary header value should be used on all responses for a given URL, including304Not Modified responses and the "default" response.

Header type	Response header

Syntax

http

Vary: *Vary: <header-name>, …, <header-nameN>

Directives

* (wildcard): Factors other than request headers influenced the generation of this response. Implies that the response is uncacheable.
<header-name>: A request header name that could have influenced the generation of this response.