What is a link relation type?

A link relation type is a registered token (the rel value) that describes how a linked resource relates to the current one — for example rel=next points to the next page, rel=canonical points to the preferred URL. The same tokens are used in HTML and elements and in HTTP Link response headers.

Where can I use link relations besides HTML?

Link relations also appear in the HTTP Link header, which carries the same rel tokens for resources that are not HTML — such as paginated JSON APIs using rel=next and rel=prev, or rel=preload hints. The syntax is defined by RFC 8288 (Web Linking).

What is the difference between rel=canonical and rel=alternate?

rel=canonical declares the single preferred URL for the current content so search engines consolidate duplicates. rel=alternate points to a different representation of the same content — another language (with hreflang), a media variant, or an RSS/Atom feed. They serve opposite purposes.

Are link relation types case-sensitive?

Registered relation types are compared case-insensitively, but by convention they are written in lowercase. Extension relations expressed as URIs are compared as-is. Stick to lowercase registered tokens for interoperability.

What is the HTTP Link Relation Types (IANA)?

A searchable reference for IANA-registered HTTP link relation types — rel values like next, prev, canonical, preload, alternate and stylesheet — each with what it describes and the spec that defines it. For HTTP Link headers and HTML rel attributes. Runs in your browser. It runs free in your browser on Gera Tools, with nothing uploaded.

HTTP Link Relation Types (IANA)

Name: HTTP Link Relation Types (IANA)
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

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This is a searchable reference for IANA-registered HTTP link relation types — the rel tokens that describe how one resource relates to another. The same registry powers HTML <link rel="..."> and <a rel="..."> elements and the HTTP Link response header (RFC 8288), so a single list covers SEO tags, resource hints, pagination, and feed discovery.

Where link relations appear

The same rel tokens are used in three places:

HTML <link> in the document head — for document-level relationships and resource hints:

<link rel="canonical" href="https://example.com/page">
<link rel="alternate" hreflang="fr" href="https://example.com/fr/page">
<link rel="preload" href="/font.woff2" as="font" crossorigin>
<link rel="stylesheet" href="/style.css">
<link rel="icon" href="/favicon.ico">

HTML <a> on a link — for link-level metadata:

<a href="https://external.com" rel="nofollow noopener noreferrer">External link</a>

HTTP Link response header (RFC 8288) — for resources that may not be HTML, and for server-driven hints:

Link: <https://api.example.com/items?page=2>; rel="next"
Link: <https://api.example.com/items?page=1>; rel="prev"
Link: </api/openapi.json>; rel="describedby"; type="application/json"

The relations that matter most

For SEO

canonical — declares the preferred URL when duplicate or near-duplicate content exists. Search engines consolidate ranking signals to the canonical. Only one per page.
alternate — points to another representation: another language (pair with hreflang), a different media format, or an Atom/RSS feed.
nofollow — tells crawlers not to pass link equity through this link. Use on user-generated content or paid links.

For performance (resource hints)

preload — fetch this resource as soon as possible; it is needed for the current page. Add as="font|style|script|image" to tell the browser what type it is.
prefetch — fetch this resource at low priority for likely next navigation.
preconnect — establish the TCP+TLS connection to this origin in advance.
dns-prefetch — resolve the DNS for this origin in advance (lighter than preconnect).
modulepreload — preload and parse a JavaScript module.

For pagination

next / prev — identify the next and previous pages in a sequence. Used in both HTML and Link headers. Search engines and API clients use these to discover and traverse all pages.
first / last — identify the first and last pages.

For security on links

noopener — prevents the opened page from accessing window.opener, stopping it from redirecting the parent tab.
noreferrer — implies noopener and additionally strips the Referer header.

Defining extension relations

Any rel value not in the IANA registry should be a full URI (an extension relation) to avoid collisions with future registered tokens:

<link rel="https://example.com/rels/tenant" href="/tenants/42">

How it works

Tokens are matched case-insensitively per the RFC. The registry and the search run entirely in your browser — nothing you type is uploaded or stored.