canonical checker

The address your
page asks to be known by.

A canonical tag is a page naming the one address it wants indexed. This reads what this page declares — in its head, in its response, or both — and says whether that claim agrees with the address the page was actually served at.

It reads one page. Whether the address it names points back, and whether anything else on your site claims the same one, are questions a second page has to answer — this does not fetch one, and says so rather than guessing.

This tool works differently from the generator. The generator never uploads your image — it runs in your browser. The checker cannot: it fetches the public address you type, from our server, and reads that page’s HTML in full, not only its head — the body is fetched and read here, then turned into findings and dropped: it is never stored, and never sent back. Only the address you enter is sent. The addresses you check are then kept in this browser, so it can tell you what changed since last time; they go nowhere, and you can clear them.