HTTP location

The HTTP Location header field is returned in responses from an HTTP server under two circumstances:

1. To ask a web browser to load a different web page (URL redirection). In this circumstance, the Location header should be sent with an HTTP status code of 3xx. It is passed as part of the response by a web server when the requested URI has:
   • Moved temporarily;
   • Moved permanently; or
   • Processed a request, e.g. a POSTed form, and is providing the result of that request at a different URI
2. To provide information about the location of a newly created resource. In this circumstance, the Location header should be sent with an HTTP status code of 201 or 202.^[1]

An obsolete version of the HTTP 1.1 specifications (IETF RFC 2616) required a complete absolute URI for redirection.^[2] The IETF HTTP working group found that the most popular web browsers tolerate the passing of a relative URL^[3] and, consequently, the updated HTTP 1.1 specifications (IETF RFC 7231) relaxed the original constraint, allowing the use of relative URLs in Location headers.^[4]

Examples

Absolute URL example

Absolute URLs are URLs that start with a scheme^[5] (e.g., http:, https:, telnet:, mailto:)^[6] and conform to scheme-specific syntax and semantics. For example, the HTTP scheme-specific syntax and semantics for HTTP URLs requires a "host" (web server address) and "absolute path", with optional components of "port" and "query".

A client requesting
https://www.example.com/index.html
using

GET /index.html HTTP/1.1 Host: www.example.com 

may get the server response

HTTP/1.1 302 Found Location: https://www.example.org/index.php 

Relative URL absolute path example

Relative URLs are URLs that do not include a scheme or a host. In order to be understood they must be combined with the URL of the original request.

A client request for
https://www.example.com/blog/all:
may get a server response with a path that is absolute because it starts with a slash:^[7]

HTTP/1.1 302 Found Location: /articles/ 

The URL of the location is expanded by the client to
https://www.example.com/articles/.^[8]

Relative URL relative path example

^[9]

A client request for
https://www.example.com/blog/latest
may get a server response with a path that is relative because it doesn't start with a slash:^[7]

HTTP/1.1 302 Found Location: 2020/zoo 

The client removes the path segment after the last slash of the original URL and appends the relative path resulting in
https://www.example.com/blog/2020/zoo.^[10][8]

See also

• URL redirection
• Post/Redirect/Get

References

1. Richardson, Leonard (2007). RESTful Web Services. Sebastopol: O'Reilly. pp. 228–230. ISBN 978-0-596-52926-0.
2. "Location". Hypertext Transfer Protocol -- HTTP/1.1. IETF. June 1999. sec. 14.30. doi:10.17487/RFC2616. RFC 2616.
3. IETF HTTPbis Working Group Ticket 185
4. "Location". Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content. IETF. June 2014. sec. 7.1.2. doi:10.17487/RFC7231. RFC 7231.
5. Uniform Resource Identifier (URI): Generic Syntax. IETF. January 2005. doi:10.17487/RFC3986. RFC 3986.
6. "IANA Uniform Resource Identifier (URI) Schemes". Retrieved 2014-11-21.
7. "Relative Reference". Uniform Resource Identifier (URI): Generic Syntax. IETF. January 2005. sec. 4.2. doi:10.17487/RFC3986. RFC 3986. Retrieved 2020-11-22.
8. "Normal Examples". Uniform Resource Identifier (URI): Generic Syntax. IETF. January 2005. sec. 5.4.1. doi:10.17487/RFC3986. RFC 3986. Retrieved 2020-11-22.
9. Uri, Aviva. Oxford Art Online. Oxford University Press. 2003. doi:10.1093/gao/9781884446054.article.t087366.
10. "Merge Paths". Uniform Resource Identifier (URI): Generic Syntax. IETF. January 2005. sec. 5.2.3. doi:10.17487/RFC3986. RFC 3986. Retrieved 2020-11-22.