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Vary header

files/en-us/web/http/reference/headers/vary/index.md

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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.

<table class="properties"> <tbody> <tr> <th scope="row">Header type</th> <td>{{Glossary("Response header")}}</td> </tr> </tbody> </table>

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.

Specifications

{{Specifications}}

Browser compatibility

{{Compat}}

See also