Vary

Vary

 


 

 

The Vary header is used by servers to inform clients what headers from a client's request will be used in server-side negotiation.[10]Its value is a list of headers that the server looks at to determine what to send the client as a response.

[10] See Chapter 17 for more on content negotiation.

An example of this would be a server that sends special HTML pages based on your web browser's features. A server sending these special pages for a URL would include a Vary header that indicated that it looked at the User-Agent header of the request to determine what to send as a response.

The Vary header also is used by caching proxies; see Chapter 7 for more on how the Vary header relates to cached HTTP responses.

Type

Response header

Basic Syntax

Vary: ("*" | 1# field-name)

Example

Vary: User-Agent

 



HTTP. The Definitive Guide
HTTP: The Definitive Guide
ISBN: 1565925092
EAN: 2147483647
Year: 2001
Pages: 294

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