Canonical Checker

A canonical tag tells search engines which URL is the “real” version of a page when the same content is reachable at several addresses (with and without www, with tracking parameters, and so on). Without one, search engines pick a version themselves and may split your ranking signals across duplicates.

Trailing-slash, http-vs-https, and www-vs-non-www differences are treated as intentional normalization and reported as such. A canonical pointing to a different host, path, or query string is flagged as a real mismatch worth investigating.

Mixed signals. If a page redirects, crawlers may never see its canonical; if a page is marked noindex but declares itself canonical, you are simultaneously saying “index this one” and “don’t index me.” The tool flags both combinations.

Yes. Relative canonicals are technically allowed but fragile — a mistake in a base URL or a scraped copy of your page can make them resolve somewhere unintended. The tool warns when the canonical is not an absolute http(s) URL.

It is strongly recommended, even when a page has no duplicates — a self-referencing canonical protects you against URL parameters and syndicated copies. The tool treats a missing canonical as a warning rather than a hard failure.