Free canonical tag checker
The canonical tag tells Google which URL is the real one when the same content lives at several addresses. Get it wrong and you can hand your ranking to a page you did not mean, or to another domain entirely. We fetch your live page and read its canonical the way Google does, then flag the classic mistakes: pointing off your own domain, conflicting tags, and relative or fragment URLs. No email.
A canonical error is a misconfigured rel="canonical" tag that causes Google to index the wrong page or split ranking signals across duplicates. Per Google's Consolidate duplicate URLs guidance, the four common failures are: cross-domain canonicals, conflicting signals, relative URLs, and canonicals outside <head>. This tool checks all four live.
free / no email / ~30s
canonical is 1 of the 164 checks in the full auditlamp audit
Fixed your tag? Read what happens after you fix a canonical tag. Google's re-evaluation typically takes 7 to 14 days.
Or paste the HTML. We read it here.
Paste your page source, or just the <head>, and we pull out every rel="canonical" and evaluate it in your browser. Nothing is sent anywhere. Add your page's real URL and we can also tell you whether the canonical points at this page or somewhere else.
What is a canonical error?
A canonical error is any misconfiguration of the rel="canonical" link element that sends Google's ranking signals to the wrong URL. Per Google Search Central, the canonical is treated as a strong hint -- not a command. When the hint is wrong or contradictory, Google resolves the conflict on its own, often choosing a version you did not intend. The four documented error types: a tag pointing to a different domain (cross-domain canonical), two conflicting tags or an HTTP Link header that disagrees with the HTML tag, a relative URL instead of an absolute one, and a tag placed outside <head> where Google ignores it. None of these errors prevent the page from loading for visitors, which is why they persist undetected for months on otherwise healthy sites.
What are canonicalization errors?
Canonicalization errors are canonical tag misconfigurations that silently hand Google's ranking credit to the wrong page. The four types from Google's documentation: cross-domain canonical, conflicting signals, relative URL, and canonical outside <head>. A fifth common mistake: combining a noindex directive with a canonical pointing elsewhere -- Google warns this sends contradictory removal signals it must resolve on its own.
One clean signal, or none. Never a contradiction.
Google treats the canonical tag as a strong hint about which URL to index and credit. The failures are rarely a missing tag; they are contradictory or misdirected tags that quietly send your ranking signals to the wrong place. Here is what we read, all grounded in Google's Consolidate duplicate URLs guidance.
- Self-referencing vs cross-domainMost pages should point their canonical at themselves. A canonical pointing at a different domain tells Google that another site is the original, and that page may never rank. We compare the canonical's host to the page's host and call it plainly.
- Conflicting canonical signalsTwo canonical tags with different URLs, or an HTTP Link header that disagrees with the HTML tag, cancel each other out. Google's guidance is that mixed signals get discarded, so it picks a version for you. One page, one canonical.
- Relative and fragment URLsGoogle recommends absolute canonical URLs. A relative path invites path-resolution mistakes, and a URL with a
#fragmentgets stripped, so the canonical you think you set is not the one Google reads. - Protocol and index contradictionsAn HTTPS page that canonicalizes to its HTTP twin hands the vote to the insecure duplicate. A page that is both noindexed and canonicalizes elsewhere sends two conflicting removal signals, which Google's docs warn against.
- The tag lives in the headA canonical outside
<head>is ignored entirely. We confirm it is where Google will actually look for it.
This checker shows whether your canonical tags are present and self-consistent. If anything fails, see the full guide to canonical errors -- it explains what each failure type means and the exact order to fix them.
Found a problem? The step-by-step repair is in our guide to how to fix canonical tag errors. Canonical trouble rarely travels alone: how to fix duplicate content with canonical tags and an accidental noindex tag cause the same wrong-page-ranks symptom, so rule out all three.
The honest version.
What is a self-referencing canonical and do I need one?
A self-referencing canonical is a rel="canonical" tag that points a page at its own URL. It is not strictly required, and Google can pick a canonical without one, but it is a low-risk best practice: it states your preferred address clearly, which helps when the same page is reachable with tracking parameters, trailing slashes, or www and non-www variants. The safe default for a normal page is a canonical pointing at its own clean, absolute URL. The exception is a page that is genuinely a duplicate of another, which should canonicalize to the original.
Does the canonical tag force Google to index that URL?
No. The canonical is a hint, not a command. Google considers your canonical alongside other signals, redirects, internal links, sitemaps, and the HTTPS version, and it can choose a different URL than the one you declared. That is why contradictions are so costly: if your canonical, your redirects, and your sitemap disagree, Google resolves the conflict on its own. To keep a page out of the index entirely, use a noindex meta tag, not a canonical, and never combine noindex with a canonical that points elsewhere.
Can a wrong canonical tag hurt my rankings?
Yes, and it is one of the quieter ways to lose visibility. A canonical pointing at your homepage from every page tells Google those pages are duplicates of the homepage, so they may drop out of results. A canonical pointing at another domain hands your ranking signals to that site. Because the page still loads normally for visitors, the mistake is invisible until you check the tag. Point each page's canonical at its own preferred URL unless it is truly a duplicate, and verify it with a checker rather than trusting that the template got it right.
Canonical is one of 164 signals. We read them all.
A clean canonical keeps your ranking signals where they belong. Whether Google and the AI engines can reach, read, trust and cite the whole page is a bigger question, and it is the one the full AuditLamp audit answers: 164 documented checks across search, answer boxes and AI assistants, ranked by what is costing you the most. Full score on screen, no email taken.