Canonical URL

The preferred version of a page, specified to search engines to prevent duplicate content issues.

A canonical URL (specified via the <link rel='canonical'> HTML tag) tells search engines which version of a page should be treated as the 'master' version for indexing and ranking purposes. It is the primary tool for managing duplicate and near-duplicate content across a site.

Canonical tags are used in many situations: when the same content is accessible at multiple URLs (e.g. with and without trailing slashes, or with URL parameters), when similar content exists across category/filter pages, or when content is syndicated across multiple sites.

If canonical tags are misconfigured, they can consolidate authority to the wrong page, preventing the intended URL from ranking. A common mistake is using a self-referencing canonical on every page without verifying it points to the correct URL — especially after URL structure changes.

Canonical tags are hints, not directives. Google may choose to ignore them if it believes a different URL is the more authoritative version. Strong internal linking to the canonical URL reinforces the signal.