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Canonical Tag Checker
Find missing or conflicting canonical signals.
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What this canonical tag checker checks and how to act on it
A canonical tag checker fetches a page and reports the rel=canonical it declares, whether that URL resolves with a 200, whether it matches the page's own URL, and whether an HTTP Link header disagrees with the HTML tag. A URL whose canonical points elsewhere is telling search engines to index a different page, which is correct for true duplicates and a silent error for everything else.
Check canonicals whenever URLs are listed in a sitemap, since non-canonical URLs should not be listed, and after any change to routing, parameters, or pagination. On sites that serve pages from more than one origin, such as a CMS plus a page platform routed under one domain, confirm every page is self-canonical on the public domain rather than on an internal host.
Read the guide
Step-by-step explanations of what this tool checks and how to fix what it finds.