What Is a Canonical URL?
Last updated 2026-09-12
A canonical URL tells search engines which version of a page is the "real" one when several URLs show the same or very similar content — preventing duplicate-content confusion and split ranking signals.
Understand the duplicate-content problem
The same content is often reachable at multiple URLs — with and without a trailing slash, with tracking parameters, on http vs https, or on both a www and non-www domain. Search engines see these as separate pages unless told otherwise.
Add a canonical tag
Place a <link rel="canonical" href="..."> tag in the <head> of every variant, pointing to the one URL you want indexed. Even the canonical page itself should point to its own URL.
Keep canonical URLs consistent site-wide
Always use the same protocol (https), the same host (with or without www, but pick one), and no unnecessary query parameters in your canonical URLs.
Example
https://example.com/shoes?color=red and https://example.com/shoes both show the same product list. Both pages set their canonical tag to https://example.com/shoes, so search engines consolidate ranking signals onto one URL.
Important Considerations
- A canonical tag is a strong hint, not a directive — search engines can still choose a different canonical if signals disagree.
- Self-referencing canonicals (a page pointing to itself) are standard practice, not redundant.
- Canonical tags don't redirect users — they only affect how search engines index the page. Use a redirect if you want users to land on a different URL.
Frequently Asked Questions
- Does a canonical tag redirect visitors?
- No — visitors still see whatever URL they requested. The canonical tag only tells search engines which version to index and rank.
- What happens if I don't set one?
- Search engines will guess which version is canonical, which can split ranking signals across duplicate URLs and occasionally pick a version you didn't intend.