deadheadmore than one rel=canonical
A page that declares more than one canonical URL has Google ignore all of them, so its duplicate URLs stop consolidating.
- Avoid
- Harmful
- Severity
- HarmfulActively breaks something for users.
- Basis
- Vendor documentationOne vendor's documentation is the source.
- Detectable
- YesMatched exactly. Autofixable when the rule carries a fix.
- Matches
logic moduleDocument rule, anywhere in the document.- Fix
- None — reports only
- Impacts
- SEO
- Related
link/sitemap
<link rel="canonical"> names the one URL that should represent a page when the same content
is reachable at several: with and without tracking parameters, with and without a trailing
slash, over http and https. It only works as a single answer. Two of them on one page
don’t split the difference. They cancel each other out.
Why avoid
Google throws them all away. Its Search Central guidance is explicit: “Specify no more than one rel=canonical for a page. When more than one is specified, all rel=canonical links will be ignored.” The page loses the one signal meant to tell Google which of its duplicate URLs should rank. Google chooses a canonical on its own, and links pointing at the different variants stop consolidating onto one URL.
The relation’s own definition asks for one. RFC 6596, which registers canonical, advises:
“Specify only one canonical link relation for a resource. (It would be confusing to
consider/label/designate more than one IRI as authoritative.)”
It almost never happens on purpose. A theme emits a canonical and an SEO plugin adds another. A CMS writes one and the layout writes one. A client-side router appends a fresh canonical on navigation without removing the server-rendered one. The two often point at different URLs, nothing on the page looks wrong, and the first sign is a Search Console report weeks later.
Use instead
One canonical, with an absolute URL, in <head>:
<link rel="canonical" href="https://example.com/dresses/green-dress"><link rel="alternate"> is for alternative versions of a page, not a second canonical.
Use hreflang for other languages and regions, and media for a separate mobile site:
<link rel="alternate" hreflang="de" href="https://example.com/de/kleider/gruenes-kleid">
<link rel="alternate" media="only screen and (max-width: 640px)" href="https://m.example.com/dresses/green-dress">Google gives the same advice: use “the appropriate link annotations to specify alternate
versions of a page”, with rel="alternate" and hreflang for language and country.
Detectability
Fully detectable, as a document rule, because a selector can’t count. Once a page has two
or more link[rel~="canonical"], every one of them is reported. Google ignores all of them,
and which to keep is the author’s decision. Identical duplicates count, since the problem is
the number of declarations. A canonical in <body> counts too: Google wouldn’t accept it on
its own, but it is still a second declaration.
There is no autofix: removing either one means choosing the canonical URL.
Resources
- Google Search Central Blog — 5 common mistakes with rel=canonical — “When more than one is specified, all rel=canonical links will be ignored.”
- Google Search Central — How to specify a canonical URL — don’t give different canonicals through different techniques; use
rel="alternate"withhreflangfor alternate versions; canonical only in<head>, with absolute URLs. - Google Search Central — Tell Google about localized versions of your page — the
<link rel="alternate" hreflang>syntax. - RFC 6596 — The Canonical Link Relation — “Specify only one canonical link relation for a resource.”
This page is generated from content/rules/head/canonical-multiple.md, the same file the linter is built from. Think the rule is wrong, or that browsers moved on? Say so — that is the most useful issue you can file.