Technical SEO
Canonical tag
Also called rel=canonical
A canonical tag is a line of HTML that tells search engines which URL is the main version of a page, when the same or very similar content is available at more than one address.
When you need one
- URLs with tracking parameters, such as ?utm_source=.
- The same page reachable with and without a trailing slash or www.
- Content syndicated on other sites.
- Product or listing pages with filters and sorting.
Best practice
Give every indexable page a self-referencing canonical, pointing to its own clean URL. It prevents duplicates from splitting your ranking signals.
Frequently asked questions
It's a strong hint. Google usually follows it, but may choose another URL if signals conflict.
Redirect when the old URL should no longer be used. Canonical when both URLs need to work for visitors.