Question 1

What does a canonical tag checker detect?

Accepted Answer

It detects missing or duplicate canonical tags, empty href attributes, relative URLs, fragments, non-HTTP schemes, whitespace, mismatched domains and canonical URLs that match the current page.

Question 2

Should a canonical URL be absolute?

Accepted Answer

Google supports relative canonical URLs, but absolute HTTPS URLs are safer because they avoid interpretation errors across hosts, protocols and staging environments.

Question 3

Can a page have more than one canonical tag?

Accepted Answer

It should not. Multiple or conflicting canonical declarations may cause search engines to ignore the signal and select another canonical URL.

Question 4

Does this tool fetch my web page?

Accepted Answer

No. Paste HTML source into the tool and all analysis runs locally in your browser, avoiding CORS limits and data uploads.