Free canonical tag checker
Inspect canonical declarations from a fetched page or pasted HTML. See the declared target, structural conflicts, and preferences that need review. Save the evidence, make a reviewed correction, then run a fresh retest. No email.
A canonical declaration expresses your preferred version of duplicate content. This checker reads HTML and HTTP Link declarations; it does not observe Google's selected canonical or prove indexing. Conflicting targets and invalid placement need attention. Cross-domain preferences can be intentional, and relative URLs are supported. Google's canonical guidance explains these distinctions.
free / no email / ~30s
canonical is 1 of the 187 registered detectors in the full auditlamp audit
want to check more than canonicals? run a full SEO audit across your whole site.
Fixed your tag? Read what happens after you fix a canonical tag. A new fetch does not establish when Google will recrawl or change its selected canonical.
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 a misconfiguration of the rel="canonical" link element that can express an unintended or conflicting duplicate preference. Per Google Search Central, the canonical is treated as a strong hint -- not a command. Google can choose a different canonical URL from the one you declare. Review conflicting targets, declarations outside the HTML head, invalid targets, and unintended duplicate relationships. A cross-domain canonical can be intentional. Relative URLs are supported, although Google recommends absolute URLs. These declaration problems need not prevent the page from loading for visitors, so normal page rendering does not verify the canonical.
What are canonicalization errors?
Canonicalization errors include conflicting or invalid declarations of a preferred duplicate URL. Examples in Google's guidance include conflicting preferences and canonical tags outside the HTML head. Cross-domain preferences need an intent review; relative URLs are supported but less robust than absolute URLs. A noindex directive concerns index eligibility, not choosing which duplicate URL to prefer. Review it separately when a page is meant to remain indexed.
One clean signal, or none. Never a contradiction.
Google treats the canonical tag as a strong hint about the preferred duplicate URL. Contradictory or unintended declarations deserve review, but a missing tag alone does not establish a canonicalization error. Here is what we read, grounded in Google's Consolidate duplicate URLs guidance.
- Self-referencing vs cross-domainA preferred version can be on this host or another host. We report the declared relationship for review rather than assume every cross-domain canonical is wrong.
- Conflicting canonical signalsTwo different canonical targets, including an HTTP Link header that disagrees with the HTML tag, express conflicting preferences. Align them with your intended duplicate relationship and inspect Google’s selected canonical separately.
- 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 contradictionsConfirm that the preferred protocol and URL match your intent. A noindex directive is not a canonicalization tool; inspect index eligibility separately. The live declaration check does not fetch the target.
- 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 review canonical preferences separately from index eligibility.
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. An unintended cross-domain canonical can express the wrong duplicate preference; Google may accept or ignore it. 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.
Check the declaration. Then verify the repair.
A clean canonical states your preferred URL clearly. The full AuditLamp audit adds technical checks and an evidence-based repair queue. It does not establish actual indexing, citations or lost revenue. Full score on screen, no email taken.