web dev//SEO//canonical

A signal that says which URL should be considered the main version of duplicated or equivalent content. "This is the official copy."

A signal that says which URL should be considered the main version of duplicated or equivalent content. "This is the official copy."

The same page often lives under several URLs: with and without trailing slash, with tracking parameters, under a print view, on http and https. The canonical tag (or header) tells the indexer to consolidate them into one entry and to credit that one.

Both URLs keep working; the visitor is not sent anywhere. That is the difference with a redirect, which actually moves the client to the other address.

It is a hint, not an order: an engine can pick another canonical if signals disagree. Consistent internal links and the sitemap should all point at the same version.