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SEO Madmanby Adam Hafez
Free tool

Canonical tag checker

Check a declared canonical URL against Google's documented rules: absolute URL, HTTPS, self versus cross-domain, and tracking parameters.

Runs entirely in your browser. Nothing you enter is uploaded, logged or stored.

Nothing you type is sent anywhere: both URLs are parsed with the browser's own URL constructor. This tool only evaluates the two URLs you give it; it cannot see your page's actual HTML, so it cannot detect a second, conflicting rel="canonical" tag if one exists.

Key takeaways

  • Google recommends an absolute URL for rel=canonical, not a relative path.
  • A self-referencing canonical and a cross-referencing canonical are both valid, but they mean different things.
  • Google's documentation names redirects and rel=canonical annotations as strong signals, and sitemap inclusion as a weak one.
  • A canonical URL that still carries tracking or session parameters defeats the purpose of consolidating duplicate URLs.
  • This tool cannot detect a second conflicting canonical tag because it only reads the two URLs you type.

What it takes

  • The page's own URL
  • The canonical URL that page declares

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How to use it

  1. 1Paste the page URL and its declared canonicalBoth need a full scheme, such as https://. Either field failing to parse is shown as an error rather than a guess.
  2. 2Check whether the canonical is absoluteGoogle's documentation recommends an absolute URL over a relative path for rel=canonical, because a relative path can cause problems if a staging or test host ever gets crawled.
  3. 3Check the HTTPS matchGoogle's documentation states it prefers HTTPS pages over equivalent HTTP pages as canonical, so a canonical pointing from HTTPS back to HTTP works against that default.
  4. 4Read the self versus cross-referencing labelA canonical that matches the page itself and one that points elsewhere are both valid uses of rel=canonical; the tool labels which case applies rather than treating either as wrong.
  5. 5Check same-domain versus cross-domainA cross-domain canonical is a documented, valid technique, but it is a stronger and riskier signal than staying on the same domain.
  6. 6Check for tracking parameters on the canonical targetGoogle's own documentation uses a tracked URL as its example of what to consolidate away from; a canonical that still carries that tracking parameter defeats the point.

Paste a page URL and the canonical URL it declares, and this tool checks the pair against Google’s own documented canonicalization guidance. Every check below traces to a specific line in that documentation rather than to general SEO advice, and nothing typed into the tool leaves the browser: both URLs are parsed with the native URL constructor.

Self-referencing versus cross-referencing canonicals

A self-referencing canonical is a page’s rel=canonical tag pointing back at itself. Google’s documentation recommends including one on the canonical page itself, alongside whatever other pages point to it as duplicates. A cross-referencing canonical points somewhere else entirely, telling Google this page is a duplicate or near-duplicate of another URL. Both are correct, documented uses of the same tag; they are just answering different questions. A self-referencing canonical says “this is the version to index.” A cross-referencing one says “index that one instead, not this one.” Confusing the two, for example by leaving a self-referencing canonical on a page that is actually a duplicate, is a common way sites accidentally tell Google to keep indexing near-identical pages separately.

The real signals Google uses when it overrides a declared canonical

Google’s documentation is explicit that a declared canonical is a hint, not a rule, and names the signals it actually weighs. Redirects and rel=canonical link annotations are both named as strong signals; a permanent redirect and an explicit canonical tag carry similar, high weight. Inclusion in a sitemap is named as a weaker signal on its own, though the documentation notes that stacking more than one of these methods toward the same target increases the odds that Google follows it. Beyond those three explicit methods, Google’s documentation lists two further signals based on site setup rather than page markup: it prefers HTTPS over an equivalent HTTP version, and it prefers a URL that is part of an hreflang cluster. None of these override a correctly declared, self-consistent canonical in ordinary cases; they matter most when a site sends Google mixed signals, such as a sitemap listing one URL while the page markup points somewhere else.

Run this check while a canonical tag is still in a draft template, before it ships to every page that template controls, since a mistake here quietly repeats across the whole site rather than showing up on a single page.

Sources

  1. 1.How to specify a canonical URL with rel="canonical" and other methods - Google Search CentralPrimary
  2. 2.What is URL canonicalization - Google Search Central
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