Vary
{{HTTPSidebar}}
The HTTP Vary {{Glossary("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 {{HTTPStatus("304")}} Not Modified responses and the “default” response.
| Header type | `{{Glossary("Response header")}}` |
|---|---|
| `{{Glossary("Forbidden header name")}}` | 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
{{Specifications}}
Browser compatibility
{{Compat}}