Vary HyperText Transfer Protocol (HTTP) response header determines how to match
future request headers. This information is required to decide whether or not a cached response can be served instead of requesting a fresh one from the origin server. This response header is used by the server to indicate the headers it used when selecting a representation of a resource in a content negotiation algorithm.
|Header type||Response header|
|Forbidden header name||no|
Vary: * Vary: <header-name>, <header-name>, ...
Each request for a URL is supposed to be treated as a unique and uncacheable request. A better way to indicate this is to use
no-store, which is clearer to read and also signals that the object should never be stored.
A comma-separated list of header names to consider when deciding whether or not a cached response can be used.
When using the
Vary: User-Agent header, caching servers should consider
the user agent when deciding whether or not to serve the page from cache. For example, if you
are serving different content to mobile users, using this header can help you to avoid a cache
mistakenly serving a desktop version of your site to your mobile users. This header can help Google
and other search engines to discover the mobile version of a page and might also tell
them that no Cloaking is intended.
|Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content (HTTP/1.1)|
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