Canonical tag

A strong hint, not a command

Duplicate URLs are normal. The same product can be reached with tracking parameters, in several categories, over HTTP and HTTPS, or with and without a trailing slash. The canonical tag tells search engines which version you want to rank.

Google says rel="canonical" is a strong signal but not a directive. It weighs the tag alongside redirects, sitemap entries, internal links and HTTPS, and may choose a different canonical if those signals disagree (consolidate duplicate URLs). Search Console’s URL Inspection shows both your declared canonical and the one Google selected.

Example

<link rel="canonical" href="https://example.com/shoes/trail-runner">

Place it in the head of every version of the page, including the main version itself, as an absolute URL.

Mistakes we see often

• Pointing at a URL that redirects or returns 404. The canonical target should return 200 and be indexable.
• Canonicalizing every paginated page to page one, which hides the products or articles listed on later pages.
• Protocol or host mismatches, such as a canonical to http:// on an HTTPS site, or to www when the site lives on the bare domain.
• Conflicting signals: the canonical says A, the sitemap lists B and internal links point to C.
• Adding or changing the canonical with JavaScript, which crawlers that do not render scripts will never see. Keep it in the server-rendered HTML.
• Canonical plus noindex on the same page, which sends contradictory instructions.

The canonical checker finds the canonical a page declares and tests whether the target resolves cleanly.