A canonical URL is the URL identified as the most representative for the page content, which in simple terms can mean the “main version”” of a page.

A good example of when canonicals are necessary is in regard to duplicate content – something that search engines try to avoid, as serving a user multiple of the same thing is never useful.

This can become an issue for eCommerce sites, which may have 100s of pages with minor differences due to filtering or sorting for users. For example, /clothes/dress?colour=black and /clothes/dress?sort=price:low may be virtually identical to each other, but also to the root /clothes/dress page. The only one that may be useful to a user searching – and therefore, the one we’d want to be indexed, is the latter; therefore, the former two pages should use the latter as the canonical URL.

Good use of canonicals helps to control the crawl budget of your website and keep the right content indexed, as well as helping when content has been syndicated to ensure it points to the original.

Return to the Glossary