~/tools/canonical-tag-checker

Canonical Tag Checker

Verify your rel="canonical" tag points to the right URL. A wrong or missing canonical tells Google to index the wrong page — or splits ranking signals across duplicates.

§ what this tool checks

Rules applied to every scan.

The canonical tag is how you tell search engines which URL is the "real" one when the same content lives at multiple addresses. Get it wrong — point it at the wrong page, another domain, or a relative path — and you can deindex pages you wanted ranked or split ranking signals across duplicates. This tool reads your canonical tag, resolves it to an absolute URL, and confirms whether it correctly references the page itself.

Presence of a rel="canonical" link tag

Canonical resolved to an absolute URL

Whether the canonical is self-referencing

Canonical pointing to a different page or domain

Canonical also declared in the HTTP Link header

Relative or malformed canonical values

§ faq

Questions, answered.

What is a canonical tag?

A canonical tag (<link rel="canonical" href="...">) tells search engines which URL is the preferred, "master" version of a page when the same or very similar content is reachable at multiple URLs. It consolidates duplicate-content signals onto one URL so ranking authority is not split across query-string variants, tracking parameters, or www/non-www duplicates.

What is a self-referencing canonical and do I need one?

A self-referencing canonical is a canonical tag that points to the page it sits on — the normal, recommended setup for any page that should be indexed on its own. It removes ambiguity for crawlers and protects against duplicate URLs created by tracking parameters. Unless a page is intentionally a duplicate of another, its canonical should point to itself.

What happens if my canonical points to the wrong page?

A wrong canonical tells Google to index a different URL instead of the current page — so the current page can effectively disappear from search while ranking signals flow to a page you did not intend. Pointing every page at the homepage, or leaving a templated canonical that points to a staging or example URL, are common and costly mistakes that can deindex large parts of a site.

Should canonical URLs be absolute or relative?

Always absolute — include the full protocol and domain (https://example.com/page), not a relative path like /page. Google can interpret relative canonicals, but they are ambiguous and easy to resolve incorrectly, especially across HTTP/HTTPS or www/non-www. An absolute canonical leaves no room for misinterpretation.

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§ other tools

Check another thing.

Single-purpose inspectors for when you need to verify one thing.

01Meta Tag CheckerCheck your page title, meta description, viewport, charset, and robots tags.02Robots.txt ValidatorValidate your robots.txt file for syntax errors and blocking rules.03AI Crawler CheckerTest if ChatGPT, Claude, and Perplexity can actually read your page — not just whether your robots.txt says they can.04Open Graph Tag PreviewCheck your Open Graph and Twitter Card tags for social media sharing.05Sitemap ValidatorValidate your sitemap.xml file format and URL count.06Heading Structure CheckerAnalyze your H1-H6 heading hierarchy for SEO best practices.07SSL Certificate CheckerCheck your SSL certificate: expiry date, issuer, and trust chain.08Redirect CheckerTrace the full redirect chain for any URL — every 301, 302, and hop.09Structured Data ValidatorValidate your JSON-LD schema markup for missing fields and errors.10Broken Link CheckerScan a page for internal links that return 404s and server errors.11Core Web Vitals CheckerCheck the lab signals behind LCP, CLS, and a fast first byte.12Security Headers CheckerScan your HTTP response headers for CSP, HSTS, and other protections.