When the same page can be reached via multiple URLs (UTM parameters, filters, sorting, trailing slash variants), search engines may treat them as duplicates and split signals. A canonical tag helps you tell crawlers which URL should be considered the primary version.
Here’s a practical checklist you can apply before publishing.
When you actually need a canonical tag
Canonical is most useful when content is identical or very similar:
- marketing links add query parameters like
?utm_...; - category pages change via filters/sorting but show largely the same listing;
- multiple host/protocol variants exist (ideally fixed with redirects, but canonical can help as a safety net);
- trailing slash vs non-trailing slash URLs.
If the pages are truly different (different language pages, different content), don’t use canonical to “merge” them.
How to choose the canonical URL
Your canonical URL should:
- return
200 OK; - be fast and not rely on redirect chains;
- be the exact URL you want to rank;
- typically be a clean version without tracking parameters.
Example: if you share https://site.com/page?utm_source=email, the canonical is usually https://site.com/page.
How to add canonical to a page
In HTML, canonical is typically placed in the <head> section:
<link rel="canonical" href="https://example.com/page" />
What to verify after implementation
- the canonical URL exists and is typed correctly;
- there is only one canonical tag per page;
- canonical doesn’t accidentally point to a different “similar” page;
- pagination strategy is deliberate (don’t blindly canonical everything to page 1 if it breaks your structure).
FAQ
Does canonical replace a 301 redirect?
No. Redirects solve access and consistency for users and bots. Canonical is a hint to search engines. In practice, redirects are preferred for hard duplicates, and canonical is helpful for parameter variations.
Is a self-referencing canonical OK?
Yes. A self-canonical is a common best practice to lock in your preferred URL.
Should I use canonical for UTM parameters?
Usually yes: if UTM URLs show the same content, the canonical should point to the clean URL without UTM.