A canonical tag is an HTML element that tells search engines which version of a page is the main one. It is used when several URLs hold very similar or identical content.
That way Google knows which page to index and to show in the results.
Why use a canonical tag?
Many websites automatically produce several variants of the same page, for example through filters, categories, tracking parameters or different URL versions.
Without a canonical tag, Google may treat these as duplicate content, which spreads your visibility across several URLs.
Typical examples:
- product pages with filters
- URLs with UTM parameters
- print versions of pages
- HTTP and HTTPS versions
- pages with and without www
A canonical tag lets you tell search engines which URL is the important one.
Why canonical tags matter
They help avoid duplicate content and concentrate the SEO signals on a single URL.
Rankings, backlinks and relevance then do not get split across several similar pages. This matters most on large websites, online shops and landing pages, where Google needs to know which page to prioritise.