Canonical URL

A canonical URL is the page address a search engine treats as the representative version when very similar content is available at multiple URLs. Website owners can indicate a preference using signals such as a canonical link element, redirects, and sitemap inclusion. For example, parameter-based URLs may display essentially the same service information as a clean main address. A canonical hint helps consolidate those versions, but Google can select a different representative URL if its systems find stronger evidence. Canonicalization is not a substitute for writing distinct content, and it does not make thin duplicate service-area pages useful. It is primarily a way to clarify which existing page version should represent the content.