Canonical URL Checker

Why duplicates happen

The same content is often reachable at many URLs: http and https, with and without www, with a trailing slash, with ?utm_source= or ?sort=price parameters, or through print and AMP versions. Without a canonical, Google picks one itself — sometimes the wrong one — and splits signals like links between the copies.

What this checker tests

• Presence — a canonical in the HTML <head> or the HTTP Link header.
• Multiple canonicals — if a page declares two different canonicals, Google ignores them all. This is common when a theme and an SEO plugin both add one.
• Self-referencing — the recommended setup for unique pages: the canonical points to the page's own clean URL.
• HTTPS — canonicals should use the secure version.
• Target status — a canonical that points to a redirect or a 404 is a contradictory signal.
• HTML vs header conflicts and noindex + canonical combinations that send mixed signals.

Correct canonical examples

<!-- On https://example.com/shoes?color=red&utm_source=mail -->
<link rel="canonical" href="https://example.com/shoes">

<!-- On the canonical page itself (self-referencing) -->
<link rel="canonical" href="https://example.com/shoes">

Common mistakes and fixes

1. Relative canonicals (href="/shoes") — allowed, but absolute URLs are safer when pages are scraped or proxied.
2. Every page canonicalised to the home page — this tells Google to ignore your other pages. Each page needs its own canonical.
3. Paginated pages canonicalised to page 1 — page 2+ have different products; give them self-referencing canonicals.
4. Canonical to a URL that redirects — point it to the final URL. Trace redirects with the Redirect Checker.
5. Canonical + noindex — pick one. Use canonical to consolidate, noindex to exclude.

Canonical is a hint, not a command

Google may choose a different canonical if your signals disagree — for example if internal links, the sitemap and hreflang all point to another version. Keep them consistent: link internally to the canonical URL, list only canonical URLs in your sitemap (check it with the Sitemap Checker), and make sure og:url matches (see the Open Graph Checker).

Frequently asked questions