The canonical tag: how to tell Google which URL to index

A canonical tag is a line in a page's HTML head that names the preferred URL for that content. Search engines use it to pick one version to index when the same page is reachable at several addresses, for example with and without tracking parameters, or with www and without.

<link rel="canonical" href="https://example.com/blue-widgets">

How Google treats it

Google treats rel="canonical" as a strong hint, not a command. It weighs it with other signals, such as redirects (a strong signal), sitemaps (a weaker one) and internal links. If signals disagree, Google may choose a different canonical. Search Console's URL Inspection tool shows which URL Google chose.

When you need one

• Every indexable page: a self-referencing canonical is a good default.
• Pages with tracking or sorting parameters.
• The same product in several categories with different URLs.
• HTTP and HTTPS, or www and non-www versions (also redirect these).
• Syndicated content republished on another site (point it at the original).

Common mistakes

1. Every page's canonical points at the homepage, which asks Google to drop the rest.
2. Relative or broken canonical URLs.
3. Canonical to a page that redirects, is noindexed or returns 404.
4. Paginated pages all canonicalized to page one, hiding the items on later pages.
5. Canonical in the HTML disagrees with one in the HTTP header.