Difference between revisions of "existing-rel-values"
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| Specifies the preferred shortened URL for the page.
| Specifies the preferred shortened URL for the page.
| [http://code.google.com/p/shortlink/wiki/Specification shortlink spec]
| [http://code.google.com/p/shortlink/wiki/Specification shortlink spec]
Revision as of 11:32, 7 June 2011
<entry-title> existing rel values </entry-title>
This page contains tables of known HTML rel values from specifications, formats, proposals, brainstorms, and non-trivial posh usage in the wild. In addition, dropped and rejected values are listed at the end for comprehensiveness.
These rel values are defined formats from specifications (HTML 4, microformats) are thus are recommended for general use. Alphabetically ordered by value.
- Do not add rel values you find in the wild to this table of rel formats, instead add them to the table in the POSH section.
- Do not add non-HTML rel values you find to this table of rel formats, instead add them to the table in the non HTML rel values section.
- Do not add rel values from obsolete/superceded proposals or drafts, instead add them to the table in the "dropped" section.
(from the relevant specification where possible)
|Link to defining specification|
|acquaintance||not allowed||external relation||the person represented by the current document considers the person represented by the referenced document to be an acquaintance||XFN - The XHTML Friends Network|
|alternate||external resource||external relation||Designates substitute versions for the document in which the link occurs. When used together with the
||HTML4 link type|
|appendix||allowed||allowed||Refers to a document serving as an appendix in a collection of documents.||HTML4 link type|
|bookmark||allowed||allowed||Refers to a bookmark. A bookmark is a link to a key entry point within an extended document. The
||HTML4 link type|
|chapter||allowed||allowed||Refers to a document serving as a chapter in a collection of documents.||HTML4 link type|
|child||not allowed||external relation||the referenced person is a child of the person represented by the current document||XFN - The XHTML Friends Network|
|colleague||not allowed||external relation||the referenced person is a colleague of the person represented by the current document||XFN - The XHTML Friends Network|
|contact||not allowed||external relation||the person represented by the current document considers the person represented by the referenced document to be a contact||XFN - The XHTML Friends Network|
|contents||allowed||allowed||Refers to a document serving as a table of contents. Some user agents also support the synonym ToC (from "Table of Contents").||HTML4 link type|
|copyright||allowed||allowed||Refers to a copyright statement for the current document.||HTML4 link type|
|co-resident||not allowed||external relation||the referenced person lives in the same residence as the person represented by the current document||XFN - The XHTML Friends Network|
|co-worker||not allowed||external relation||the referenced person is a co-worker of the person represented by the current document||XFN - The XHTML Friends Network|
|crush||not allowed||external relation||this person considers the referenced person to be a crush (i.e. has a crush on the referenced person)||XFN - The XHTML Friends Network|
|date||not allowed||external relation||this person considers the referenced person to be a date (i.e. is dating the referenced person)||XFN - The XHTML Friends Network|
|friend||not allowed||external relation||the person represented by the current document considers the person represented by the referenced document to be a friend||XFN - The XHTML Friends Network|
|glossary||allowed||allowed||Refers to a document providing a glossary of terms that pertain to the current document.||HTML4 link type|
|help||allowed||allowed||Refers to a document offering help (more information, links to other sources information, etc.)||HTML4 link type|
|index||allowed||allowed||Refers to a document providing an index for the current document.||HTML4 link type|
|kin||not allowed||external relation||the referenced person is part of the extended family of the person represented by the current document||XFN - The XHTML Friends Network|
|license||allowed||allowed||…indicates that the [referenced document] is a license for the current page.||rel="license"|
|me||external relation||external relation||the referenced document represents the same person as does the current document||XFN - The XHTML Friends Network|
|met||not allowed||external relation||this person has met the referenced person||XFN - The XHTML Friends Network|
|muse||not allowed||external relation||the referenced person inspires the person represented by the current document||XFN - The XHTML Friends Network|
|neighbor||not allowed||external relation||the referenced person lives nearby the person represented by the current document||XFN - The XHTML Friends Network|
|next||external relation||external relation||Refers to the next document in a linear sequence of documents. User agents may choose to preload the "next" document, to reduce the perceived load time.||HTML4 link type|
|nofollow||external relation||external relation||indicates that the destination of that hyperlink SHOULD NOT be afforded any additional weight or ranking by user agents which perform link analysis upon web pages (e.g. search engines).||rel="nofollow"|
|parent||not allowed||external relation||the referenced person is a parent of the person represented by the current document||XFN - The XHTML Friends Network|
|prev||external relation||external relation||Refers to the previous document in an ordered series of documents. Some user agents also support the synonym "Previous".||HTML4 link type|
|previous||external relation||external relation||Synonym of
||HTML4 link type|
|section||allowed||allowed||Refers to a document serving as a section in a collection of documents.||HTML4 link type|
|sibling||not allowed||external relation||the referenced person is a sibling of the person represented by the current document||XFN - The XHTML Friends Network|
|spouse||not allowed||external relation||the referenced person is a spouse of the person represented by the current document||XFN - The XHTML Friends Network|
|start||allowed||allowed||Refers to the first document in a collection of documents. This link type tells search engines which document is considered by the author to be the starting point of the collection.||HTML4 link type|
|stylesheet||external resource||not allowed||a style sheet for the current document
used with the invisible <link href> element which is not ideal for content relationships. Content relationships should be user visible and thus uses with <a href> are strongly preferred. Unfortunately the use of stylesheet in user visible content like <a href> appears to be strictly theoretical.
|HTML4 link type|
|subsection||allowed||allowed||Refers to a document serving as a subsection in a collection of documents.||HTML4 link type|
|sweetheart||not allowed||external relation||this person considers the referenced person to be their sweetheart||XFN - The XHTML Friends Network|
|tag||not allowed||allowed||…indicates that the [referenced document] is an author-designated "tag" (or keyword/subject) for the current page.||rel="tag"|
||HTML4 link type|
|transformation||allowed||allowed||Relates a source document to a transformation, usually represented in XSLT, that relates the source document syntax to the RDF graph syntax. Used in GRDDL||GRDDL spec|
rel="alternate"can take further meaning from additional attributes, such as
rel="alternate" lang="fr"(French language version of this page)
rel="alternate" media="print"(printable version of this page)
rel="alternate" media="handheld"(version of the page intended or better for handheld/portable devices like PDAs, cell phones, etc.)
- Synonyms such as "previous", "toc" are not as widely supported as the main term.
A few rel values have been developed as drafts as a result of going through most of the microformats The microformats process, and are thus listed here for your serious consideration. You may use these values, and if you find any problems with them please point them out on the respective "issues" page for the rel value.
|rel value||summary||proposed in||external spec (if any)|
|pronunciation||…indicates that the destination of the 'link' element is a document providing a pronunciation lexicon for speech-synthesis purposes.||rel-pronunciation|
|directory||…indicates that the destination of the hyperlink is a directory listing containing an entry for the current page.||rel-directory|
|enclosure||…indicates that the destination of that hyperlink is intended to be downloaded and cached.||rel="enclosure"||RFC4287|
|home||…indicates that the [referenced document] is the homepage of the site in which the current page appears.||rel="home"|
Several rel values are being brainstormed as potential microformats and are thus listed here. If you find you have a use for such semantics in real world examples, consider trying out these values and provide feedback on the respective brainstorming page(s) with your results and experiences.
You may list new proposed rel values here, and even better if you can list and link to POSH uses in the wild.
|rel value||summary||brainstormed in and usage in the wild|
|accessibility||indicate[s] that the destination of that hyperlink contains accessibility information for the current page.||blog post which itself uses the rel value in a <link> tag in the head of the document.|
|bibliography||indicate[s] that the destination of that hyperlink is a bibliography for the current page.||mailing list post, 2007-10-15|
|cite||indicate[s] that the destination of that hyperlink is an authoritative source or a precedent to the current page.||distributed-conversation-brainstorming|
|group||the referenced document represents a group to which the person represented by the current document belongs||Group Brainstorming
|longdesc||Alternative to the img longdesc attribute, for use on visible links||Google search for rel=longdesc in the wild shows many sources of proposals. Please edit this to list the earliest and perhaps most recent/comprehensive proposal. No known real world POSH usage in the wild yet.|
|map||Link to a map. Possibly embedded within an adr, hCard, geo or hCalendar. Parsers MAY attempt to parse the URL if it is a link to a known map site (e.g. Geohash, Google Maps, Multimap) and extract co-ordinates and other useful data.||(to TobyInk by email)|
|member||the referenced document represents a member of the group represented by the current document||Group Brainstorming|
|profile||indicate[s] that the destination of that hyperlink is a metadata profile (e.g. an XMDP profile) for the current page or portion thereof||XMDP Brainstorming|
|shortlink||the referenced document represents the current document but with a shorter URL||blog post|
|vcalendar-parent||link from an event to a containing event||hCalendar 1.1 draft|
|vcalendar-child||link from an event to a contained event||hCalendar 1.1 draft|
|vcalendar-sibling||link from an event to a related event with the same container||hCalendar 1.1 draft|
|status||the referenced document represents the status (or source of status updates) for the author of this document||blog post|
- Genealogy Brainstorming for some thoughts on possible additional values for family relationships (use existing XFN - The XHTML Friends Network parent, child, sibling, spouse, kin values first though)
- xpn-brainstorming for some thoughts on possible additional values for professional relationships (use existing XFN - The XHTML Friends Network co-worker, colleague values first though)
There are numerous rel values used as posh, both in the wild, whose origins are not necessarily known, nor are their meanings consistent. There are also numerous rel values from external proposals of varying degrees of merit. It is useful to document their existence and summarize their implied meanings/usage intent as research that may be used to perhaps take one or more of them thru the microformats The microformats process if there is both sufficient interest and sufficient in the wild usage.
Note: this list is incomplete, please help complete it from the following sources:
- Meta Information in DevMo Docs (DevMo)
- Web Communication Link Relationships (WCLR)
- W3C Link Relationship values draft (LRdraft) - from a draft of the HTML spec circa 1991.
- HTML5 draft Liable to change
- FOAF Project Wiki: Autodiscovery (FOAF)
- Google Blog
|archive||index of archived entrigs||unknown, perhaps Wordpress open source blogging software||WCLR|
|archives||Provides a link to a collection of records, documents, or other materials of historical interest.||HTML5|
|author||…||unknown||DevMo / HTML5|
|canonical||To help search engines disambiguate the same page with multiple representations||Google/Microsoft/Yahoo!, Ask Jeeves
|EditURI||Used by "blog client" software for automating posting and updating blog content from your desktop.||Seen in WordPress, e.g. . Probably used by other blog content management systems as well.||…|
|external||Indicates that the referenced document is not part of the same site as the current document.||…||HTML5|
|feed||Gives the address of a syndication feed for the current document.||…||WCLR/ HTML5|
|first||Indicates that the current document is a part of a series, and that the first document in the series is the referenced document.||…||HTML5|
|icon||Imports an icon to represent the current document. (Allowed in
|lightbox||…||(Google search for rel=lightbox in the wild)||…|
|meta||…||1999 W3C RDF syntax REC||FOAF|
|microsummary||…||…||Microsummary, be aware of: microsummary issues|
|noreferrer||indicates that no referrer information is to be leaked when following the link.||HTML5||HTML5|
|openid.delegate||…||(Google search for rel=openid.* in the wild)||…|
|openid.server||…||(Google search for rel=openid.* in the wild)||…|
|pgpkey||(see also rel-publickey)||…||, |
|pingback||Gives the address of the pingback server that handles pingbacks to the current document. (Allowed in
|prefetch||Specifies that the target resource should be pre-emptively cached. (Allowed in
|publickey||(see also rel-pgpkey)||…|||
|replies||indicates a continued thread||unknown||RFC4685|
|sidebar||Specifies that the referenced document, if retrieved, is intended to be shown in the browser's sidebar (if it has one).||HTML5|
|trackback||…||unknown, perhaps open source Movable Type blogging software||WCLR|
|unendorsed||(probably redundant to nofollow)||…||WCLR|
|up||Provides a link to a document giving the context for the current document.||…||HTML5|
|wlwmanifest||Used by "Windows Live Writer," a Microsoft blog client for automating posting and updating blog content from your desktop.||Seen in WordPress, e.g. . Probably used by other blog content management systems as well.||…|
The WCLR proposal is described by its author (in e-mail, 2007-09-25) as:
…now effectively obsolete, since HTML5 and Microformats cover all the worthwhile relationships in that already.
These are covered by HTML5 already:
- permalink -> bookmark
- archive -> archives
- unendorsed -> nofollow
The rest now seem unnecessary.
Nonetheless, there may be some mileage in using them in microformats, at least until HTML5 is widely available.
The following values are registered as link type extensions per the requirements in the WHATWG HTML spec and the requirements in the W3C HTML5 spec. Please make sure that registrations added here have all the required data filled in including "Effect on link", "Effect on a and area" and a link to a spec. Note that entries in the Formats table excluding entries from HTML 4 (which HTML5 supercedes) and entries that are already in HTML5 as built-in keywords are also considered extensions with the "Approved" status. Also note that changes to this registry may not be reflected in validators in real time.
||Brief description||Link to specification||Synonyms||Status|
|apple-touch-icon||External Resource||Not allowed||Specify a Webpage Icon for a “Web Clip”, or “touch icon”, for mobile devices (not limited to Apple devices).||Apple's Safari Web Content Guide||probably redundant with rel=icon||proposed|
|apple-touch-icon-precomposed||External Resource||Not allowed||Specify a Webpage Icon for a “Web Clip”, or “touch icon”, for mobile devices (not limited to Apple devices).||Apple's Safari Web Content Guide||probably redundant with rel=icon||proposed|
|apple-touch-startup-image||External Resource||Not allowed||Specify a splashscreen for Web apps on iOS Safari||Apple's Safari Web Content Guide||maybe redundant with rel=icon with the sizes attribute?||proposed|
|canonical||External Resource||Not allowed||Specifies the canonical URL for the current document in order to help avoid duplicate content.||Canonical meta tag Canonicalization at Google Webmaster Central Microsoft Webmaster Center Yahoo! Search Blog||proposed|
|dns-prefetch||External Resource||Not allowed||Tells the browser to perform dns lookup for host names ahead of use.||Mozilla documentation Google documentation||proposed|
|openid.delegate||External Resource||Not allowed||When the page that contains the link is used as an OpenID indentifier, the relying party perform sOpenID 1.1 authentication with the link target as the identifier instead.||OpenID Authentication 1.1||proposed|
|openid.server||External Resource||Not allowed||The OpenID server for the relying party to contact for OpenID 1.1 authentication||OpenID Authentication 1.1||proposed|
|openid2.local_id||External Resource||Not allowed||When the page that contains the link is used as an OpenID indentifier, the relying party perform sOpenID 2.0 authentication with the link target as the identifier instead.||OpenID Authentication 2.0||proposed|
|openid2.provider||External Resource||Not allowed||The OpenID server for the relying party to contact for OpenID 2.0 authentication||OpenID Authentication 2.0||proposed|
|prerender||External Resource||Not allowed||Prerenders the Web page targeted by the link including running it scripts.||Chrome Prerendering||proposed|
|service||External Resource||Not allowed||Atom Publishing Protocol editing service autodiscovery.||Documentation on the WHATWG wiki||proposed|
|shortcut||External Resource||Not allowed||Used as a companion for
||Documentation on MSDN||proposed|
|shortlink||External Resource||Not allowed||Specifies the preferred shortened URL for the page.||shortlink spec||proposed|
|timesheet||External Resource||Not allowed||Applies a timesheet to the document.||non-normative section in the Timesheet spec||proposed|
non HTML rel values
There are markup languages other than HTML that also have a rel attribute, often based upon the HTML rel attribute. It is useful to document some of these other languages and their rel values for both reference purposes, and to provide background research for the possible development and re-use of these values in HTML, as poshformats or microformats
- rfc-4287 rfc-4287 specification.
- See http://www.iana.org/assignments/link-relations.html for more.
(from the relevant specification where possible))
|in-reply-to||See http://code.google.com/apis/youtube/2.0/developers_guide_protocol_comments.html||YouTube + Atom|
The following rel values were in earlier version(s) of specification(s) and it is presumed by their absence from the most recent version of the respective specification(s) that they have been deprecated or obsoleted. Use of them could be considered a bit more standard than just POSH, although you may wish to research why such values were omitted from latter specifications before using them. If you do discover the reasoning, please add a short statement or link to thereof into the appropriate place in the following table.
In general, you SHOULD NOT use any dropped values.
In addition, if any such values have been superceded by standard values (see the first table on this page), then you MUST NOT use the dropped versions.
- HTML3 (HTML3) / has been superceded by HTML 3.2 - which itself has been superceded by HTML 4.0 - which itself has been updated by HTML 4.01, commonly referred to as "HTML 4" in this wiki and other places.)
- Proposed HTML 4.0 link types (HTML4dropped) - obsoleted/superceded by the HTML 4.0 Recommendation. Any values that were in the "Proposed HTML 4.0 link types" document but didn't make it into the HTML 4.0 Recommendation were thus explicitly dropped and should be avoided.
|rel value||summary||defining specification||why dropped|
|banner||Was used to reference another document to be used as banner for this document (i.e. a form of "include" statement).||HTML3||unknown|
|begin||identifies the author-defined start of a sequence of documents of which the current document is a node.||HTML4dropped||unknown|
|biblioentry||identifies a bibliographic entry||HTML4dropped||unknown|
|bibliography||identifies a bibliography||HTML4dropped||unknown|
|child (obsolete/superceded)||the target document is a hierarchical child, or subdocument, of the current document||HTML4dropped||unknown|
|citation||the target is a bibliographic citation||HTML4dropped||unknown|
|collection||the target document is an collection that contains the current document||HTML4dropped||unknown|
|definition||identifies a definition of a term||HTML4dropped||unknown|
|disclaimer||identifies a hypertext link to a legal disclaimer||HTML4dropped||unknown|
|editor||identifies a hypertext link to an editor||HTML4dropped||unknown|
|end||identifies the author-defined end of a sequence of documents of which the current document is a node.||HTML4dropped||unknown|
|footnote||the anchor is a footnote marker and the target is a footnote||HTML4dropped||unknown|
|navigate||the target document contains information such as a image map that will help users to gain a sense of how and where to found information||HTML4dropped||unknown|
|parent (obsolete/superceded)||the target document is the hierarchical parent, or container, of the current document||HTML4dropped||unknown|
|pointer||the target is a pointer to the real target. This value can be used by a user agent to perform a pre-fetch of the specified target for evaluation until the real target is reached||HTML4dropped||unknown|
|publisher||identifies a hypertext link to a publisher||HTML4dropped||unknown|
|sibling (obsolete/superceded)||the target document is a child of a common parent, or a hierarchical peer of the current document||HTML4dropped||unknown|
|top||the target document is the logical top node of the tree (see also
|trademark||identifies a hypertext link to a trademark notice||HTML4dropped||unknown|
|translation||the target is a translation to another language||HTML4dropped||unknown|
|up||When the document forms part of a hierarchy, this link references the immediate parent of the current document.||HTML3||unknown, but proposed for re-introduction in HTML5|
|urc||identifies a Universal Resource Citation||HTML4dropped||unknown|
Some rel values have been proposed and rejected. They are listed here to make that explicit. Authors MUST NOT use rejected rel values.
|rel value||origin / proposal||why rejected|
Some rel values have been added to this page perhaps in one of the tables above, but no examples, nor an actual specification explicitly stating that the value(s) should be used in the HTML4 'rel' attribute could be found. They are listed here in the hopes someone can discover more specific/precise URLs to examples or specifications about them (preferably both). Until such precise URLs to examples/specs are provided, the values can be treated as they are purely theoretical and thus of little interest.
- Dublin Core. This search may help: .
- examples from that search only use invisible
<link href>element. At first glance it appears the results from the search show only uses with the invisible
<link href>element which is not ideal for content relationships. Content relationships should be user visible and thus uses with
<a href>are strongly preferred.
- RFC2731 defines
rel="schema.RC"with the pattern
rel="schema.PREFIX"as a syntax for defining namespaces for use in meta[@name], *[@rel], *[@rev] and (as per eRDF) *[@class] attributes. A link to a Dublin Core metadata schema is generally not suitable for end users, so
<link href>appears to be more appropriate than
<a href>for those that use Dublin Core metadata schemas.
- RFC2731 defines
- proposal to use in content currently only theoretical. Thus unfortunately the use of Dublin Core in user visible content like
<a href>appears to be strictly theoretical. See microformats-discuss/2008-January/011445.html for a proposal to use Dublin Core in user visible content.
- examples from that search only use invisible
- existing rel values
- rel examples
- rel FAQ
- rel design pattern
- rel values issues
- rel registry