existing-rel-values
<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.
usage: see how is 'rel' used. Regarding rev, see: should 'rev' even be used.
formats
These rel values are defined formats from specifications (HTML 4, microformats) are thus are recommended for general use. Alphabetically ordered by value.
Note:
- 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- Do not add rel values from obsolete/superceded proposals or drafts, instead add them to the table in the "dropped" section.
Sources:
- W3C HTML 4 link type and GRDDL specs.
- xfn and other microformats
| rel value | summary (from the relevant specification where possible)) |
defining specification |
|---|---|---|
| acquaintance | the person represented by the current document considers the person represented by the referenced document to be an acquaintance | XFN |
| alternate | Designates substitute versions for the document in which the link occurs. When used together with the lang attribute, it implies a translated version of the document. When used together with the media attribute, it implies a version designed for a different medium (or media). |
HTML4 link type |
| appendix | Refers to a document serving as an appendix in a collection of documents. | HTML4 link type |
| bookmark | Refers to a bookmark. A bookmark is a link to a key entry point within an extended document. The title attribute may be used, for example, to label the bookmark. Note that several bookmarks may be defined in each document. |
HTML4 link type |
| chapter | Refers to a document serving as a chapter in a collection of documents. | HTML4 link type |
| child | the referenced person is a child of the person represented by the current document | XFN |
| colleague | the referenced person is a colleague of the person represented by the current document | XFN |
| contact | the person represented by the current document considers the person represented by the referenced document to be a contact | XFN |
| contents | 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 | Refers to a copyright statement for the current document. | HTML4 link type |
| co-resident | the referenced person lives in the same residence as the person represented by the current document | XFN |
| co-worker | the referenced person is a co-worker of the person represented by the current document | XFN |
| crush | this person considers the referenced person to be a crush (i.e. has a crush on the referenced person) | XFN |
| date | this person considers the referenced person to be a date (i.e. is dating the referenced person) | XFN |
| friend | the person represented by the current document considers the person represented by the referenced document to be a friend | XFN |
| glossary | Refers to a document providing a glossary of terms that pertain to the current document. | HTML4 link type |
| help | Refers to a document offering help (more information, links to other sources information, etc.) | HTML4 link type |
| index | Refers to a document providing an index for the current document. | HTML4 link type |
| kin | the referenced person is part of the extended family of the person represented by the current document | XFN |
| license | …indicates that the [referenced document] is a license for the current page. | rel-license |
| me | the referenced document represents the same person as does the current document | XFN |
| met | this person has met the referenced person | XFN |
| muse | the referenced person inspires the person represented by the current document | XFN |
| neighbor | the referenced person lives nearby the person represented by the current document | XFN |
| next | 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 | 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 | the referenced person is a parent of the person represented by the current document | XFN |
| prev | Refers to the previous document in an ordered series of documents. Some user agents also support the synonym "Previous". | HTML4 link type |
| previous | Synonym of prev |
HTML4 link type |
| section | Refers to a document serving as a section in a collection of documents. | HTML4 link type |
| sibling | the referenced person is a sibling of the person represented by the current document | XFN |
| spouse | the referenced person is a spouse of the person represented by the current document | XFN |
| start | 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 | 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 | Refers to a document serving as a subsection in a collection of documents. | HTML4 link type |
| sweetheart | this person considers the referenced person to be their sweetheart | XFN |
| tag | …indicates that the [referenced document] is an author-designated "tag" (or keyword/subject) for the current page. | rel-tag |
| toc | Synonym of contents (from "Table Of Contents") |
HTML4 link type |
| transformation | 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 |
notes
rel="alternate"can take further meaning from additional attributes, such asrel="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.
proposals
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) |
|---|---|---|---|
| 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 | … | rel-payment |
brainstorming
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.
| rel value | summary | brainstormed in |
|---|---|---|
| accessibility | indicate[s] that the destination of that hyperlink contains accessibility information for the current page. | blog post |
| 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 |
| 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 |
| product | … | product-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 |
more brainstorming
See also:
- 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)
POSH usage
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: this list is incomplete, please help complete it from the following sources:
External sources:
- Meta Information in DevMo Docs (DevMo)
- Microsummary
- 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)
- RFC4685
- Google Blog
| rel value | summary | origin | proposal(s) |
|---|---|---|---|
| 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 | … | unknown | DevMo / HTML5 |
| canonical | To help search engines disambiguate the same page with multiple representations | Google/Microsoft/Yahoo!, Ask Jeeves
| |
| comment | … | … | WCLR |
| contribution | … | … | WCLR |
| details | … | (seen on w3c.org news log in a "read more" permalink) | … |
| EditURI | … | Seen in WordPress, e.g. [1] | … |
| endorsed | … | … | WCLR |
| external | Indicates that the referenced document is not part of the same site as the current document. | … | HTML5 |
| fan | xxxx. | … | hcard-user-profile-authoring |
| 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 link only) |
… | WCLR/ HTML5 |
| lightbox | … | (Google search for rel=lightbox in the wild) | … |
| made | … | … | LRdraft |
| meta | … | 1999 W3C RDF syntax REC | FOAF |
| microsummary | … | … | Microsummary, be aware of: microsummary issues |
| openid.delegate | … | (Google search for rel=openid.* in the wild) | … |
| openid.server | … | (Google search for rel=openid.* in the wild) | … |
| permalink | … | … | WCLR |
| pgpkey | (see also rel-publickey) | … | [2], [3] |
| pingback | Gives the address of the pingback server that handles pingbacks to the current document. (Allowed in link only) |
… | WCLR/ HTML5 |
| prefetch | Specifies that the target resource should be pre-emptively cached. (Allowed in link only) |
… | HTML5 |
| publickey | (see also rel-pgpkey) | … | [4] |
| referral | … | … | WCLR |
| related | … | … | WCLR |
| replies | indicates a continued thread | unknown | RFC4685 |
| resource | … | … | WCLR |
| search | … | unknown | unknown |
| sidebar | Specifies that the referenced document, if retrieved, is intended to be shown in the browser's sidebar (if it has one). | HTML5 | |
| sponsor | … | … | WCLR |
| 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 |
| user | … | … | WCLR |
| via | … | … | WCLR |
WCLR
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
- feed
- pingback
- 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.
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
Sources:
- Atom RFC4287 specification.
- See http://www.iana.org/assignments/link-relations.html for more.
| rel value | summary (from the relevant specification where possible)) |
defining specification |
|---|---|---|
| self | See http://www.rfc-editor.org/rfc/rfc4287.txt | Atom |
| ... | ... | ... |
dropped
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.
Sources:
- 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 |
| first | synonym for begin |
HTML4dropped | unknown |
| footnote | the anchor is a footnote marker and the target is a footnote | HTML4dropped | unknown |
| last | synonym for end |
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 top |
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 begin) |
HTML4dropped | unknown |
| 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 |
rejected
Some rel values have been proposed and rejected. They are listed here to make that explicit. Authors MUST NOT use rejected rel values.
Source: rejected-formats.
| rel value | origin / proposal | why rejected |
|---|---|---|
| pavatar | pavatar | rejected-formats#Pavatar |
unspecified
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.
| rel value | summary | source |
|---|---|---|
| schema.DC | … | Dublin Core |
| schema.DCTERMS | … | Dublin Core |
Notes:
- Dublin Core. This search may help: [5].
- 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.AC"andrel="schema.RC"with the patternrel="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
tools
See implementations.