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Via header

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

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The Via {{glossary("request header", "request")}} and {{glossary("response header")}} is added by {{Glossary("Proxy_server", "proxies")}}, both forward and reverse. It is used for tracking message forwards, avoiding request loops, and identifying the protocol capabilities of senders along the request/response chain.

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

Syntax

http
Via: [<protocol-name>/]<protocol-version> <host>[:<port>]
Via: [<protocol-name>/]<protocol-version> <pseudonym>

Directives

  • <protocol-name> {{optional_inline}}
    • : The name of the protocol used, such as "HTTP".
  • <protocol-version>
    • : The version of the protocol used, such as "1.1".
  • <host>
    • : Public proxy URL and optional <port>. If a host is not provided, then a <pseudonym> must be used.
  • <pseudonym>
    • : Name/alias of an internal proxy. If a pseudonym is not provided, then a <host> must be used.

Examples

http
Via: 1.1 vegur
Via: HTTP/1.1 GWA
Via: 1.0 fred, 1.1 p.example.net

Specifications

{{Specifications}}

Browser compatibility

{{Compat}}

See also