Canonical presence
The presence of a rel=canonical tag is checked, and a missing canonical is reported with context, since a self-referencing canonical is the safe default on most pages.
Multiple canonicals
Multiple conflicting canonical tags are detected, because two different canonical URLs on one page make Google ignore both.
Absolute URL
The canonical href is checked for being a fully-qualified absolute URL, since a relative canonical is a common and damaging mistake.
Self vs cross-domain
The canonical is classified as self-referencing, same-site, or cross-domain, because a cross-domain canonical hands authority to another site.
Target resolution
The canonical target is fetched one hop to confirm it returns HTTP 200, since a canonical pointing to a dead page tells Google the authoritative version does not exist.
Canonical chains
The target is checked for declaring a different canonical of its own, because a canonical chain may cause Google to ignore the signal entirely.
Canonical tags are how a site consolidates duplicate-content signals onto one URL. A wrong canonical is one of the most damaging silent SEO errors: a canonical pointing every page at the homepage can deindex an entire site, and a canonical to a 404 tells Google the real version is gone. Canonicalization does not guarantee rankings, but a broken canonical actively destroys them by scattering or discarding the authority a page has earned.
Missing canonical
A missing canonical is fixed by adding a self-referencing rel=canonical pointing at the page's own preferred URL. A self-referencing canonical is the recommended default for most pages.
Multiple canonicals
Multiple canonical tags are fixed by removing all but one, since conflicting canonicals cause Google to ignore the signal completely.
Relative canonical
A relative canonical is fixed by replacing it with the full absolute URL (https://…). Canonicals must be fully qualified to be reliable.
Canonical to a dead page
A canonical pointing to a non-200 URL is fixed by pointing it at a URL that resolves successfully, because Google treats a dead canonical as the authoritative version not existing.
Canonical chain
A canonical chain is fixed by pointing the canonical directly at the final URL rather than at a page that itself canonicalizes elsewhere.
Unintended cross-domain canonical
An accidental cross-domain canonical is fixed by pointing the canonical back to a URL on the same site, unless syndication to another domain is genuinely intended.
What is a canonical tag?
A canonical tag is a rel="canonical" link that tells search engines which URL is the authoritative version of a page when duplicate or similar URLs exist.
Should every page have a canonical tag?
Most pages benefit from a self-referencing canonical, which removes ambiguity for search engines even when no obvious duplicates exist.
What is a canonical chain?
A canonical chain happens when a page's canonical points to a second URL that itself canonicalizes to a third URL. Google may not follow chains, so the signal can be lost.
Can a canonical tag deindex my site?
A misconfigured canonical can effectively deindex pages, most commonly when every page canonicalizes to the homepage, which tells Google the other pages are not distinct.
Is a cross-domain canonical bad?
A cross-domain canonical is correct only for intentional syndication, because it tells Google the authoritative version lives on a different site and that page should rank instead.
Does a canonical guarantee which URL ranks?
A canonical is a strong hint, not a directive. Google usually respects it but can choose a different canonical if other signals strongly disagree.
Is this canonical checker free?
Our Canonical Tag Checker is free, with no sign-up, no limits, and nothing stored. The page you submit is fetched server-side, analyzed, and then discarded.