Canonical Tag Validator
Paste your page’s HTML — the whole document or just the <head> — and the validator finds the canonical tag and flags the problems that quietly cost rankings.
This validator runs entirely in your browser. Nothing you paste is sent to our server, so nothing is saved.
What the validator checks
The validator reads the HTML you paste and looks for the rel="canonical" link element. It then reports the essentials and flags the issues search engines care about: whether a canonical is present, whether there is more than one (which can cause them all to be ignored), whether the URL is absolute and uses https://, whether the tag sits in the <head> (a canonical in the body is ignored), and whether the URL contains a fragment. Enter the page’s own URL to also check whether the canonical is self-referencing.
How to read the result
A green result means the canonical is present and, if you supplied the page URL, self-referencing — the recommended baseline for a page that should stand on its own. A neutral result means the canonical points elsewhere, which is correct for a duplicate or variant but should be deliberate. Each warning names a specific fix. For the underlying rules, see the rel=canonical syntax reference and common canonical tag mistakes. To test a page that is already live, use the Canonical Tag Checker; to build a new tag, use the Canonical Tag Generator.
Privacy
This tool is entirely client-side. The HTML and URL you enter are processed in your browser with JavaScript and are never transmitted to or stored on our server.
Frequently asked questions
Does the validator send my HTML anywhere?
No. It runs entirely in your browser, so nothing you paste is transmitted to or stored on our server.
Do I need to paste the whole page?
No. The <head>, or even just the canonical tag, is enough for the validator to find and check it.
What does the validator flag as a problem?
A missing canonical, more than one canonical, a relative or non-HTTPS URL, a canonical in the body instead of the head, or (if you enter the page URL) a canonical that is not self-referencing.
Why does it say my canonical is not self-referencing?
Because the canonical URL does not match the page URL you entered. That is correct for a duplicate or variant, but should be intentional.