Canonical Tags Explained: When and How to Use Them
In shortA canonical tag tells Google which version of a page is the main one. Every indexable page should point to itself, and duplicates should point to the original.
The same content often lives at several URLs: with and without a trailing slash, with tracking parameters, in print versions, or in several product categories. Without guidance, Google picks one itself — and may pick the wrong one. The canonical tag is your guidance:
<link rel="canonical" href="https://example.com/page/">When you need canonicals
- URL parameters: ?utm_source=, ?sort=price, ?color=red.
- E-commerce products reachable from several categories — see faceted navigation and duplicate content.
- Content syndicated to other sites.
- HTTP/HTTPS or www/non-www versions that still resolve.
Five common mistakes
- Canonical to a redirected URL. Point to the final 200 URL only.
- Canonical to a noindex page. Conflicting signals; Google may ignore both.
- All pages canonical to the homepage. A theme bug I still see. It tells Google every page is a duplicate of your homepage.
- Paginated pages canonical to page 1. Page 2 has different content; let it point to itself.
- Canonical in the body or added twice. It must be in the head, once. Two plugins often print two.
Canonical is a hint, not a command
Google can ignore your canonical if other signals disagree — internal links, sitemap entries, redirects. Keep them consistent: link internally to the canonical version and list only canonical URLs in your sitemap.
How to check
Use Search Console’s URL Inspection tool: it shows the “User-declared canonical” and the “Google-selected canonical”. If they differ on important pages, investigate.
Canonical conflicts are among the most common issues in my technical & on-page SEO audits.
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