Technical SEO · Glossary
What is a canonical tag?
A canonical tag is a link element (rel=canonical) in a page's HTML that tells Google which URL you prefer as the main version when several URLs show the same or very similar content. Google treats it as a strong hint, not a rule, and may select a different canonical.
Written by Noor KhanWhy Canonical tag matters
Duplicate URLs are normal: tracking parameters, filters, sort orders, HTTP and HTTPS versions. Without a clear canonical, Google picks one itself, and it may not be the URL you want ranked and reported.
How Canonical tag works
- Google groups pages with the same or very similar main content and picks one to show in search.
- Redirects, rel=canonical, sitemaps and HTTPS all feed that choice; redirects are the strongest signal and sitemaps a weak one.
- Search Console's URL Inspection tool shows both your declared canonical and the one Google selected.
How to apply it
- Add a self-referencing canonical to every indexable page.
- Point parameter and variant URLs at the main version.
- Keep canonicals, internal links, redirects and the sitemap pointing at the same URL.
- Use a 301 redirect instead when the duplicate URL doesn't need to exist.
Example
An online store's product appears at /products/blue-mug and /collections/mugs/products/blue-mug. Both declare /products/blue-mug as canonical, and every internal link and the sitemap use that URL too.
Common mistake
Using noindex or robots.txt to handle duplicates. Google advises against both for canonicalization, and noindex removes the page from Search entirely.
put this into practice