Canonical (rel=canonical)
An HTML tag pointing search engines to the preferred version of a page when duplicates exist.
Full definition
Canonical (rel=canonical) is an HTML tag that tells search engines which is the "primary" version of a page when identical or near-duplicate content is accessible at multiple URLs.
Example: a page accessible via http://, https://, www., and non-www. — canonical points to one version as the authority.
Syntax: <link rel="canonical" href="https://site.com/page/" />
- •Common use cases:
- •URL parameter duplicates (?sort=price, ?color=red).
- •HTTP vs HTTPS versions.
- •Pagination pages (canonical to page 1 or self-referencing).
- •Cross-domain canonical (for content syndication).
- •International versions (hreflang is usually preferred over canonical for this).
Common mistake: canonical pointing to a noindex page or a 301 redirect — in both cases, Google may ignore the signal.