What's a canonical tag actually for?

It tells search engines which version of a page (when duplicates or near-duplicates exist, like with/without URL parameters) should be treated as the primary one for indexing and ranking.

What does it mean if a page has no canonical tag at all?

Search engines will guess which version to treat as canonical, which isn't guaranteed to match your preference — adding an explicit tag removes that ambiguity.

What if a page has multiple canonical tags?

That's a conflict most search engines don't handle predictably — a page should only ever have exactly one canonical tag.

Does Canonical URL Checker upload my files to a server?

No. Canonical URL Checker runs entirely in your browser using on-device processing, your files never leave your device.

Canonical URL Checker

Check a page's HTML for a missing, duplicate, or mismatched canonical tag.

Runs in your browser

Page URL (optional, to check it’s self-referencing)Page HTML (paste the <head> section, or the whole page)

About this tool

A missing, duplicate, or incorrectly pointed canonical tag can cause search engines to index the wrong version of a page, or split ranking signals across what should be treated as one page — a subtle issue that doesn't break anything visibly but quietly hurts SEO. This tool checks a page's HTML for exactly these canonical tag problems, catching an issue that's easy to overlook since it has no visible symptom on the page itself.

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