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 proposed rel values for HTML5 here, add them to the HTML5 link type extensions table.
- 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- Do not add rel values from obsolete/superceded proposals or drafts, instead add them to the table in the "dropped" section.
- W3C Recommendations:
- HTML 4.01 section 6.12 Link types (HTML4 Link types)
- Gleaning Resource Descriptions from Dialects of Languages (GRDDL)
- microformats specifications
|Keyword|| Effect on || Effect on || Brief description |
(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|
|alternate||external resource||external relation|| Designates substitute versions for the document in which the link occurs. When used together with the ||HTML4 Link types|
|appendix||allowed||allowed||Refers to a document serving as an appendix in a collection of documents.|| HTML4 Link types
|bookmark||not allowed||allowed|| Refers to a bookmark. A bookmark is a link to a key entry point within an extended document. The ||HTML4 Link types|
|chapter||allowed||allowed||Refers to a document serving as a chapter in a collection of documents.||HTML4 Link types|
|child||not allowed||external relation||the referenced person is a child of the person represented by the current document||XFN|
|colleague||not allowed||external relation||the referenced person is a colleague of the person represented by the current document||XFN|
|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|
|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 types|
|copyright||allowed||allowed||Refers to a copyright statement for the current document.||HTML4 Link types|
|co-resident||not allowed||external relation||the referenced person lives in the same residence as the person represented by the current document||XFN|
|co-worker||not allowed||external relation||the referenced person is a co-worker of the person represented by the current document||XFN|
|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|
|date||not allowed||external relation||this person considers the referenced person to be a date (i.e. is dating the referenced person)||XFN|
|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|
|glossary||allowed||allowed||Refers to a document providing a list of terms and their definitions that pertain to the current document.||HTML4 Link types|
|help||allowed||allowed||Refers to a document offering help (more information, links to other sources information, etc.)||HTML4 Link types|
|its-rules||allowed||not allowed||Refers to a document with external ITS rules.||Internationalization Tag Set (ITS) Version 2.0|
|kin||not allowed||external relation||the referenced person is part of the extended family of the person represented by the current document||XFN|
|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|
|met||not allowed||external relation||this person has met the referenced person||XFN|
|muse||not allowed||external relation||the referenced person inspires the person represented by the current document||XFN|
|neighbor||not allowed||external relation||the referenced person lives nearby the person represented by the current document||XFN|
|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 types|
|nofollow||not allowed||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|
|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 types|
|previous||external relation||external relation|| Synonym of ||HTML4 Link types|
|section||allowed||allowed||Refers to a document serving as a section in a collection of documents.||HTML4 Link types|
|sibling||not allowed||external relation||the referenced person is a sibling of the person represented by the current document||XFN|
|spouse||not allowed||external relation||the referenced person is a spouse of the person represented by the current document||XFN|
|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 types|
|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 types|
|subsection||allowed||allowed||Refers to a document serving as a subsection in a collection of documents.||HTML4 Link types|
|sweetheart||not allowed||external relation||this person considers the referenced person to be their sweetheart||XFN|
|tag||not allowed||allowed||…indicates that the [referenced document] is an author-designated "tag" (or keyword/subject) for the current page.||rel-tag|
|toc||allowed||allowed|| Synonym of ||HTML4 Link types|
|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|
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 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|
|payment||…indicates that the destination of the hyperlink provides a way to show or give support (e.g. financial) for the current page||rel-payment|
HTML5 link type extensions
Before you register a new value:
- Please check the Formats table and DO NOT re-register rel values that are already there. Please note that the W3C HTML WG has made a Decision to drop
lastfrom the HTML5 spec itself.
- Please check the Dropped table and DO NOT register values that are already there. If you believe a rel value was dropped from another specification without prejudice, please provide link/cite to explicit text/decision stating as such, e.g. the value was merely postponed, or perhaps expected to be spun-out into its own spec from the group developing that specification.
Note that entries in the Formats table and entries that are already in HTML5 as built-in keywords are also considered extensions with the "Ratified" status.
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 that documents the keyword as an HTML
relkeyword. (A spec that merely defines the file format of the link target but does not define the
relkeyword for use in HTML is not the kind of spec that is being required here.)
Entries lacking any of the above required data will likely be removed.
Changes to this registry may not be reflected in validators in real time.
If you add a rel value to this table and you want it supported in the validator(s), you need to either open a validator bug or e-mail the email@example.com list to ask that it be added and reference your change to this page.
|Keyword|| Effect on || Effect on ||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|
|attachment||Hyperlink||Hyperlink||The resource linked to is "attached" to this document, similar to email attachments. Used in WordPress.||No formal specification||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|
|category||Hyperlink||Hyperlink||Refers to a category assigned to the current document or post. Implemented by WordPress for indicating a relation between a blog post and a category.||rel-category||proposed|
|component||External Resource||Not allowed||Specify an HTML document that is treated as a component of this document.||Web Components||proposed|
|chrome-webstore-item||External Resource||Not allowed||Link tag to declare for app and extensions inline installations hosted in the Chrome Web Store.||Using Inline Installation||proposed|
|disclosure||Not allowed||External Resource||The 'disclosure' Link Relation Type designates a list of patent disclosures or a particular patent disclosure itself made with respect to material for which such relation type is specified.||The 'disclosure' Link Relation Type||proposed|
|discussion||Hyperlink||Hyperlink||Refers to discussion of the current document or post.||rel-discussion|| 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|
|edit||Hyperlink||Not allowed||Tells the browser where the current page can be edited||Universal Edit Button Alternate Linking Scheme. Implemented in at least MediaWiki.||proposed|
|EditURI||External Resource||Not allowed||A blogging auto discovery value, commonly used by WordPress||AtomAPI||proposed|
|entry-content||Not allowed||External Resource||Indicates that the referenced document is an alternative display source for an Internet Explorer Web Slice.||Web Slice format specification 0.9||proposed|
|external||Not allowed||Hyperlink||Indicates that the referenced document is not part of the same site as the current document.||rel-external||proposed|
|home||Hyperlink||Hyperlink||Refers to the top level document for the current document. It can be combined with 'alternate' to indicate a feed for the site of the current page.||rel-home||proposed|
|hub||Hyperlink||Hyperlink||Refers to a hub that enables registration for notification of updates to the current page.||PubSubHubbub Spec||proposed|
|in-reply-to||Hyperlink||Hyperlink||Refers to an original post that the current page is a comment on or reply to.||rel-in-reply-to||proposed|
|index||Hyperlink||Hyperlink||Refers to a document providing a list of topics with pointers that pertain to the current document.||HTML4||proposed|
|indieauth||External Resource||Not allowed||the IndieAuth server for the relying party to contact for IndieAuth authentication||IndieAuth specification||proposed|
|issues||Hyperlink||Hyperlink||Refers to issues regarding the current document or specification.||rel-discussion||proposed|
|lightbox||Not allowed||Img Pop-Up|| Images with this attribute are displayed in a larger way than embedded in a website (or how you specified it) when clicked (e.g. with installed "Lightbox 2"-Plugin). When adding [group] to rel="lightbox" all images get a clickable button for next/prev; insert into ||Lightbox 2 (needs actual specification to be kept in this list, this link is just documentation of one implementation)||proposed|
|manifest||External Resource||Not allowed||Imports or links to a manifest||W3C Manifest for web application||proposed|
|meta||External Resource||Not allowed||External metadata about the HTML document||W3C's RDF/XML Syntax Specification||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|
|pgpkey||External Resource||Not allowed||Associates a PGP key with a Web page so that the Web page URL can be used as the commenter's URL in PGP-signed blog comments and the blogging system receiving the comment can fetch the key and verify the signature as belonging to the owner of the URL.||PGP-Signed Comments||proposed|
|pingback||External Resource||Not allowed||gives the address of the pingback server that handles pingbacks to the current document||Pingback||proposed|
|prerender||External Resource||External Resource||Prerenders the Web page targeted by the link including running it scripts.||rel-prerender||proposed|
|profile||External Resource||Contextual External Resource||indicate[s] that the destination of that hyperlink is a metadata profile (e.g. an XMDP profile) for the current page or portion thereof. See also xmdp-brainstorming.||rel-profile||proposed|
|publisher||External Resource||External Resource||Indicates that the referenced document is a metadata profile (e.g., a social-media/real-name profile such as a Google+ profile) for the publisher of the current page, or some portion of the current page.||Google help page||proposed|
|rendition||External Resource||External Resource||Indicates some example rendering, interpretation, or depiction of the source. User agents may choose to execute, display, or render the target in-place; or navigate to the target.||HTML rel rendition|| proposed
|service||External Resource||Not allowed||Atom Publishing Protocol editing service autodiscovery.||Documentation on the WHATWG wiki||proposed|
|shortlink||External Resource||Not allowed||Specifies the preferred shortened URL for the page.||shortlink spec||proposed|
|sidebar||Hyperlink||Hyperlink||Indicates that the referenced document is intended to be shown in a secondary browsing context.||rel-sidebar|| proposed
|sitemap||External Resource||Not allowed||Provides a link to an XML document describing the layout of the site.||rel-sitemap||proposed|
|subresource||External Resource||Not allowed||An external resource intended for use within the current page.||Chromium documentation||proposed|
|syndication||Hyperlink||Hyperlink||Refers to a page which is a syndicated copy of the current page.||rel-syndication||proposed|
|timesheet||External Resource||Not allowed||Applies a timesheet to the document.||non-normative section in the Timesheet spec||proposed|
|webmention||External Resource||Hyperlink||gives the address of the webmention endpoint that handles webmentions to the current document||WebMention specification||proposed|
|widget||External Resource||External Resource||Autodiscovery for W3C widgets||non-normative section in the Widget packaging spec||proposed|
|wlwmanifest||External Resource||Not allowed||Windows Live Writer manifest autodiscovery||documentation on MSDN||proposed|
|image_src||External Resource||Not allowed||Specify a Webpage Icon for use by Facebook, Yahoo, Digg, etc.||Unknown, but see for instance this||probably redundant with rel=icon||proposed|
|http://docs.oasis-open.org/ns/cmis/link/200908/acl||External Resource||External Resource||Identifies the resource containing a CMIS ACL document for the link context||CMIS 1.0, Section 220.127.116.11||proposed|
|stylesheet/less||External Resource||Not allowed||Less CSS framework stylesheets.||Less CSS usage|| proposed
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.|
|author||indicate[s] that the destination of that hyperlink represents the author of the current page. Combines with rel-me to chain authorship information.|| Google has said it will index rel-Author in this blog post, with further discussion of the rel-me connection See also the HTML5 spec
|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|
|preconnect||indicates an origin that will be used to fetch required resources. Initiating an early connection, which includes the DNS lookup, TCP handshake, and optional TLS negotiation, allows the user agent to mask the high costs of connection establishment latency.||resource hints draft|
|prefetch||indicates the URL and content-type of a resource that is likely to be a required resource when the next action or navigation is triggered. Initiating an early fetch allows the user agent to mask the request latency of the resource and make it available sooner to the application.||resource hints draft|
|preload||indicates the URL and content-type of a resource that should be fetched as early as possible by the user agent. Initiating an early fetch allows the user agent to mask the request latency of the resource and make it available sooner to the application.||resource hints draft|
|prerender||indicates the URL of the next navigation target. Initiating a prerender allows the user agent to deliver an instant navigation experience: the user agent downloads the top-level resource and its assets, and performs all of the processing steps required to show the page without actually showing it to the user.||resource hints draft|
|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|
|source||the referenced document represents the source code for the current document or project||source-brainstorming 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 parent, child, sibling, spouse, kin values first though)
- xpn-brainstorming for some thoughts on possible additional values for professional relationships (use existing XFN 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 process if there is both sufficient interest and sufficient in the wild usage.
Note: If a value is missing from this table, it may have either already been promoted by writing it up as a proposal, or demoted by being explicitly dropped. Please check the other tables first before adding to this table.
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 entries||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||see brainstorming above for suggested use by google||unknown||DevMo / HTML5|
|canonical||To help search engines disambiguate the same page with multiple representations||Google/Microsoft/Yahoo!, Ask Jeeves|
|EditURI||Location of the xml-rpc gateway for a Wordpress install that allows external programs to add, edit and delete posts. Used by "WordPress blog client" software for automating posting and updating blog content from your desktop.||Seen in WordPress, e.g. .||Description stubbed in rel-edituri.|
|feed||Gives the address of a syndication feed for the current document.||…||WCLR/ HTML5|
|footnote||Location of the footnote on a link to a footnote.||Markdown preprocessors such as Maruku||HTML5|
|icon|| Imports an icon to represent the current document. (Allowed in ||HTML5||WCLR/HTML5|
|kinetic-stylesheet||Imports a KSS 'kinetic stylesheet' to bind dynamic behavior to elements||Used in the Plone Content Management System||…|
|lightbox|| Hook - Indicates that following the link will trigger a "lightbox" script (Allowed in ||(Google search for rel=lightbox in the wild)||…|
|lightbox[group_name]||Used by lightbox scripts to group different sets of images together. Images from one group will not appear in another group's lightbox. See also "lightbox".||Lightbox 2||…|
|prettyPhoto||See also "lightbox"||(Google search for rel="prettyphoto" in the wild)||…|
|clearbox||See also "lightbox"||(Google search for rel="clearbox" 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 ||…||WCLR/ HTML5|
|popover||Used by a JS widget to display a large, descriptive tooltip.||Twitter's Bootstrap Popover.js||…|
|prefetch|| Specifies that the target resource should be pre-emptively cached. (Allowed in ||…||HTML5|
|publickey||(see also rel-pgpkey)||…|||
|replies||indicates a continued thread||unknown||RFC4685|
|sitemap||Links to a site map document.||…||http://www.sitemaps.org/|
|tooltip||Used by a JS widget to display a tooltip similar (though more customizable) to what is shown by browsers if the 'title' attribute is present.||Twitter's Bootstrap Tooltip.js (and likely other JS tools)||…|
|trackback||…||unknown, perhaps open source Movable Type blogging software||WCLR|
|unendorsed||(probably redundant to nofollow)||…||WCLR|
|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. . Similar values are 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.
In the past, Dublin Core values have been added to this page in the table about HTML5 features, but no examples, nor an actual specification explicitly stating how the value(s) should be used in HTML could be found. The linked specifications below have been updated so we should start considering Dublin Core values accordingly.
|schema.DC||a specification of all metadata terms maintained by the Dublin Core Metadata Initiative, with regard to the fifteen terms of the Dublin Core Metadata Element Set already published||Dublin Core|
|schema.DCTERMS||a specification of all metadata terms maintained by the Dublin Core Metadata Initiative, reflecting the changes described more fully in the 2012 document "Maintenance changes to DCMI Metadata Terms" ||Dublin Core|
Issues need updating given new information from linked resources.
- 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.
- The scheme proposed above provides metadata namespace declarations. As described by DCMI specifications, such indications cannot be provided w/o a suitable namespace. In order to give complete pieces of information, the correct description set must be:
<link rel="schema.DCTERMS" href="http://purl.org/dc/terms/">(for the namespace declaration, followed by)
<meta name="DCTERMS.[element]" content="[element.value]">for related elements.
- 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.
- recent improvements. DCMI solves some trouble concerning metadata through the description set model. Some of these informations cannot currently be provided in any standard ways other than DC, namely dates, validity and periodicity. Following this public bug report (), the correct namespace declaration for DC and DCTERMS metadata are now considered valid HTML code. We must encourage this practice both for internal usefulness and for shared practices.
- examples from that search only use invisible
- The Dublin Core document "Expressing Dublin Core metadata using HTML/XHTML meta and link elements" is a specification for, and gives examples of, both <link rel="schema.DC" href="http://purl.org/dc/elements/1.1/"> and <link rel="schema.DCTERMS" href="http://purl.org/dc/terms/">. Note that Dublin Core encourages the use of DCTERMS elements over DC. A list of projects which use Dublin Core metadata is maintained here.
- "Expressing Dublin Core metadata using HTML/XHTML meta and link elements" also includes examples of <link rel="DCTERMS.[element]" href="">, where [element] = subject, isReferencedBy, creator, and publisher. The <link> tag is used instead of the <meta> tag whenever the content is a URL. (Note that this use is different from, but related to, <link rel="schema.DCTERMS" href="">.) Potentially, any of the 55 DCTERMS elements could be used in this way, and this could include use in HTML 5.
- As said before, HTML5 validators now allow the use of
<link rel="schema.DCTERMS" href="http://purl.org/dc/terms/">for namespace declarations.
- As said before, HTML5 validators now allow the use of
Use with HTTP Link Header
You can also use any of the rel values (that are allowed for link elements) with HTTP Link Headers,
Link: <http://creativecommons.org/publicdomain/zero/1.0/>; rel="license"
For multiple licenses (e.g. CC-SA and GPL), simply use multiple
Link: <http://creativecommons.org/licenses/by-sa/3.0/>; rel="license" Link: <http://www.gnu.org/licenses/gpl.html>; rel="license"
Example: similarly, linking to a copyright statement for an image:
Link: <http://example.org/copyright.html>; rel="copyright"
or providing a brief inline copyright statement:
Link: <data:text/plain;charset=utf-8,Copyright 2013 ExampleCo, All Rights Reserved.>; rel="copyright"
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 HTML '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.
A simple list here is sufficient.
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
- Atom RFC4287 specification.
- See http://www.iana.org/assignments/link-relations.html for more.
- See Maze+XML
- See Collection+JSON
- See OpenSearch
- See The Create-Form and Edit-Form Link Relations (RFC6861)
|rel value|| summary|
(from the relevant specification where possible))
|self|| From http://www.ietf.org/rfc/rfc4287.txt : |
The value "self" signifies that the IRI in the value of the href attribute identifies a resource equivalent to the containing element.
|http://gdata.youtube.com/schemas/2007#in-reply-to||See http://code.google.com/apis/youtube/2.0/developers_guide_protocol_comments.html||YouTube extension to Atom|
|collection|| Refers to a resource which represents a collection of which the current resource is a member.
When used in the Maze+XML media type, the associated URI returns the available collection of mazes.
| Maze+XML, Collection+JSON, OpenSearch
|east|| Refers to a resource to the "east" of the current resource.
When used in the Maze+XML media type, the associated URI points to a neighboring cell resource to the east in the active maze.
|exit|| Refers to a resource that represents the exit or end of the current client actvity or process.
When used in the Maze+XML media type, the associated URI points to the final exit resource of the active maze.
|north|| Refers to a resource that is "north" of the current resource.
When used in the Maze+XML media type, the associated URI points to a neighboring cell resource to the north in the active maze.
|south|| Refers to a resource that is "south" of the current resource.
When used in the Maze+XML media type, the associated URI points to a neighboring cell resource to the south in the active maze.
|via||Identifies a resource that is the source of the information in the context.|| Atom 1.0 Syndication format (RFC 4287)
|west|| Refers to a resource that is "west" of the current resource.
When used in the Maze+XML media type, the associated URI points to a neighboring cell resource to the west in the active maze.
|item||The target IRI points to a resource that is a member of a collection represented by the context IRI.||Collection+JSON|
|create-form||When included in a resource, the "create-form" link relation MAY identify a target resource that represents the form to append a new member to the link context.||See The Create-Form and Edit-Form Link Relations (RFC6861)|
|edit-form||When included in a resource, the "edit-form" link relation identifies a target resource that represents the form for editing associated resource.||See The Create-Form and Edit-Form Link Relations (RFC6861)|
|lightframe||Opens the target in a lightbox. On inclusion it provides a simple target the lightframe and loads the content in a lightbox effect||Lightbox|
|superbox[image]||jQuery Superbox! is a script which allows you display windows with the lightbox effect.||superbox|
|wp-video-lightbox||wp-video-lightbox! is a rel to anchor tag script display videos with the lightbox effect.||wp-video-lightbox|
|youtube||Opens the target youtube video in using the Swipebox Plugin||Swipebox|
|shadowbox||shadowbox is a jQuery script for images displaying with the "lightbox" effects.||shadowbox|
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.
In general, you SHOULD NOT use any dropped values.
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.
- if a rel value was in a draft and is missing (without explanation) from the final spec, or
- if a rel value was in a previous version of and is missing (without explanation) from an update to the specification (even a draft update)
Then absent any other information or explanation, it is presumed that the group/editors working on that specification decided to explicitly drop it (either in development, or in the updated version) and thus it should be obsoleted (not re-registered).
If you wish to add them, please research why such values were omitted from latter specifications before doing so. If you do discover the reasoning, please add a short statement or link to thereof into the appropriate place in the following table.
If there is more data, e.g. a link to an email of discussion of the spec development that explains why the rel value was dropped, and it explicitly states, e.g. it was without prejudice, or merely post-poned, or perhaps expected to be spun-out into its spec (or some other explicit positive reason), then it makes to link/cite that explicit text as part of a proposal.
- 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|
|origin|| synonym for ||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 ||HTML4dropped||unknown|
|trademark||identifies a hypertext link to a trademark notice||HTML4dropped||unknown|
|translation||the target is a translation to another language||HTML4dropped||unknown
|urc||identifies a Universal Resource Citation||HTML4dropped||unknown|
dropped without prejudice
In one known instance (from HTML4 to HTML5), some rel values were in an earlier version of a specification (or a proposal) and were dropped from a latter (draft) version, and it was noted that these values were dropped with the intent that they could still be proposed in a registry and thus they explicitly were not deprecated or obsoleted. This section documents such values as separate from the dropped section.
In general, you SHOULD NOT use any dropped values.
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.
Rel values that were dropped without prejudice from a specification will be considered similar to new values that have never been specified.
If you know of additional rel values that were dropped without prejudice from an update to a specification, please cite a URL and quote from the group developing the specification that officially states from that group that the dropping of the values was done without prejudice, or equivalent statement (such as explicit allowance of external registration, proposal, and/or development).
This table serves a historical purpose. If you wish to propose a value from this table, please copy it and leave it in place.
- Several rel values were explicitly dropped from HTML5. Per: Issue 118 Decision (emphasis added):
"The final proposal argues for the removal of some relation values, to wit, it suggests removal of index, up, first and last. It was pointed out in survey comments that these relations are already registered in the IANA link relation registry. Presumably, these relations could also be entered in whatever other registry or registries HTML5 adopts for this purpose....
"Since the relations to be removed are already registered at the IANA link relation registry, no further action is needed to include them there. WG members are free to register or record these relations elsehwere [sic], as well."
|rel value||summary||defining specification||why dropped|
|first|| synonym for ||HTML4dropped - never in an official spec||Explicitly dropped from HTML5 interim draft yet permitted for external registry|
|index||Refers to a document providing an index for the current document.||was in HTML4||Explicitly dropped from HTML5 interim draft yet permitted for external registry|
|last|| synonym for ||HTML4dropped - never in an official spec||Explicitly dropped from HTML5 interim draft yet permitted for external registry|
|up||When the document forms part of a hierarchy, this link references the immediate parent of the current document.||was in HTML3 - but dropped in HTML4||Explicitly dropped from HTML5 interim draft yet permitted for external registry|
See related HTML5: Link types for existing HTML5 specified rel values.
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|
addtional external research
Here are some additional historical references to the development or rel-values which may be useful when researching values, especially why specific values may have been proposed but abandoned.
- 1996-06-07 Hypertext links in HTML (copies: ftp.ics.uci.edu)
- 1996-11-13 Describing and Linking Web Resources
- 1997-01-23 LYNX-DEV Lynx and the LINK tag
- 1997-01-24 Taxonomy list
- 1997-03-28 W3C Working Draft: Hypertext Links and Meta Information in HTML
previous attempts at documenting
There have been previous attempts at documenting known rel values, most of which fell out of date due to being dependent on a single author maintaining them. They're listed here purely for historical reasons, and are not sufficient to be references of their own (since they're just individual curations of other references)
- Link Type Definitions Glossary by fantasai
- existing rel values
- rel examples
- rel FAQ
- rel design pattern
- rel values issues