Canonical Tag
An HTML element that tells search engines which URL is the master copy when the same or similar content exists at multiple addresses.
Definition
A canonical tag is a `<link rel="canonical">` element placed in a page's `<head>` that nominates a single preferred URL for content that may be reachable via several different addresses.
When the same or similar content is reachable through more than one URL — through tracking parameters, session IDs, mobile and desktop variants, http vs https, or trailing slashes — search engines have to choose which version to index. A canonical tag is the page's own statement of which URL to treat as authoritative. Google considers it a strong hint, not a directive, and may still pick a different canonical if other signals (sitemap entries, internal links, redirects) point elsewhere.
Examples
Same product reached via two URLs
An e-commerce site lists the same shoe at /shoes/runner and /collections/sale/runner. The sale URL adds a canonical tag pointing to /shoes/runner so search engines consolidate ranking signals on the primary page.
Self-referencing canonical
Most pages declare themselves canonical with `<link rel="canonical" href="https://example.com/about" />` so URL parameters appended by ad campaigns don't fragment indexing.
Sources
Related terms
Where QueryCatch uses this
Last updated: 2026-05-10