Link relation

HTML
Comparisons

A link relation is a descriptive attribute attached to a hyperlink in order to define the type of the link, or the relationship between the source and destination resources. The attribute can be used by automated systems, or can be presented to a user in a different way.

In HTML these are designated with the rel attribute on link, a, or area elements. Example uses include the standard way of referencing CSS, <link rel="stylesheet" href="example.css" />, which indicates that the external resource linked to with the href attribute is a stylesheet, so a web browser will generally fetch this file to render the page. Another example is rel="shortcut icon" for the popular favicon icon.[1][2]

Link relations are used in some microformats (e.g. rel="tag" for tagging), in XHTML Friends Network (XFN), and in the Atom standard, in XLink, as well as in HTML. Standardized link relations are one of the foundations of HATEOAS as they allow the user agent to understand the meaning of the available state transitions in a Representational State Transfer system.

The Internet Engineering Task Force (IETF) has a registry of standardized link relations,[3] and a procedure for extending it defined in RFC 5988. HTML5 also defines valid link relations.[4]

In HTML4, the rev attribute of a link is also defined, which defines the relationship between the resources. The attribute is removed in HTML5.

  1. ^ Dubost, Karl (October 2005). "Web site meta data profile: favicon, …". World Wide Web Consortium. Retrieved 23 February 2011.
  2. ^ Dubost, Karl (24 October 2005). "How to Add a Favicon to your Site". World Wide Web Consortium. Retrieved 25 February 2011.