Via header

The Via request and response header is added by 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.

Syntax

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

Directives

<protocol-name> Optional

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

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

Specifications

• HTTP Semantics

See also

• X-Forwarded-For
• Heroku's proxy library Vegur