What is a canonical tag and why is it important?

A canonical tag (<link rel="canonical">) tells search engines which version of a page should be treated as the original when multiple URLs have similar or duplicate content.

Source: Screaming Frog

For example, example.com/shoes and example.com/shoes?color=red may contain nearly identical content. Without a canonical, Google could index both, splitting ranking signals.

By declaring a canonical, you consolidate link equity, avoid duplicate content penalties, and make it clear which URL should appear in search results. This is especially critical for eCommerce sites with filters and parameters.