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CanonicalCheck

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Canonical tag checker

Check the canonical URL of any page online. We read rel="canonical" from both the HTML head and the HTTP Link header, follow redirects first, and test it against Google's rules.

What the validator tests

  1. The page returns 200 once redirects are followed.
  2. A canonical exists, in the HTML <head> or the HTTP Link header.
  3. It sits in the head. Google ignores rel="canonical" in the body.
  4. There is only one canonical URL. Conflicting values can get all of them ignored.
  5. The URL is absolute, not relative.
  6. It does not downgrade HTTPS to HTTP.
  7. It is self-referencing, or it points elsewhere on purpose (cross-domain flagged).
  8. No stray query parameters the page doesn't have.
  9. The page is not also noindex.
  10. On request: the target itself returns 200 without redirecting.

A correct canonical tag

<head>
  <link rel="canonical"
        href="https://example.com/mugs/blue/">
</head>

For PDFs and other non-HTML files, send it as a header instead:

Link: <https://example.com/guide.pdf>; rel="canonical"

Remember that rel="canonical" is a strong hint, not a command. Google weighs it with redirects, sitemaps, internal links and HTTPS, as described in Google Search Central's guide to consolidating duplicate URLs. See how the signals combine.

Questions

How do I check the canonical URL of a page?

Enter the page URL above. The checker follows any redirects, then reads the rel="canonical" link in the HTML head and any canonical in the HTTP Link header, and shows the resolved absolute URL. Manually, you can view the page source and search for rel="canonical".

Should every page have a self-referencing canonical?

Google does not require it, but recommends specifying a canonical for duplicate pages, and a self-referencing canonical is a cheap way to make the preferred URL explicit when tracking parameters or alternate hosts create copies of the page.

Why is Google ignoring my canonical tag?

rel="canonical" is a hint. Google may choose another URL if the canonical is in the body, conflicts with another canonical, points at a redirect, a 404 or a noindexed page, or disagrees with stronger signals such as redirects, internal links and the sitemap. Search Console's URL Inspection tool shows the Google-selected canonical.

Can the canonical point to another domain?

Yes. Cross-domain canonicals are supported, for example for syndicated content. The checker flags them so you can confirm they are intentional.

Does this tool render JavaScript?

No. It reads the HTML the server sends. Google says it can process canonicals injected with JavaScript, but recommends putting them in the initial HTML, so a missing canonical here is worth fixing even if a script adds one later.