What is a canonical URL?

A canonical URL is specified via a link rel=canonical tag in the HTML head. It tells search engines which URL is the preferred version when duplicate or similar content exists at multiple URLs.

Why is the canonical tag important for SEO?

Without canonical tags, Google may split link equity between duplicate pages such as HTTP vs HTTPS or www vs non-www versions. Canonicalization consolidates ranking signals to one URL.

What is a self-referential canonical?

A self-referential canonical is when a page canonical tag points to itself. This is best practice as it explicitly tells Google this URL is the preferred version even when no duplicates exist.

When should I use a canonical instead of a 301 redirect?

Use a canonical when content is intentionally accessible at multiple URLs such as product pages with filters. Use a 301 redirect when you permanently move content to a new URL and want to retire the old one.

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Canonical URL Checker

Check if any URL has a canonical tag, verify self-referential canonicals, detect missing or broken canonical tags. Essential for SEO and avoiding duplicate content issues.

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📋 Manual Canonical Tag Checker

Paste your page's HTML source to check for canonical tags without making a request:

What is a Canonical Tag?

A canonical tag (<link rel="canonical" href="...">) tells search engines which URL is the "master" or preferred version of a page when there are multiple URLs with similar or identical content. This prevents duplicate content penalties and consolidates link equity.

Common Canonical Tag Issues

Missing canonical — Search engines may index duplicate versions
Self-referential canonical — Correct: points to the page itself
Cross-domain canonical — Consolidates syndicated content
Incorrect canonical — Points to wrong URL (causes lost traffic)
Noindex with canonical — Conflicting signals confuse search engines

Canonical URL Checker

What is a Canonical Tag?

Common Canonical Tag Issues

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