Vary
The HTTP Vary response 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 a Vary header ensures that responses are separately cached based on the headers listed in the Vary field.
Most often, this is used to create a cache key when content negotiation is in use.
The same Vary header value should be used on all responses for a given URL, including 304 Not Modified responses and the "default" response.
| Header type | Response header |
|---|---|
| Forbidden request header | No |
Syntax
Either * as a wildcard, or one or more header names in a comma-separated list:
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.
Specifications
Browser compatibility
See also
- Content negotiation
- HTTP caching: Vary
- Understanding The Vary Header on smashingmagazine.com (2017)
- Best Practices for Using the Vary Header on fastly.com