04 / Forge / SEO / Server-side
Canonical checker
Resolve a page's canonical URL and check it is absolute, single, self-referencing, and https. Fetches the target through the engine's validated fetcher: public http and https addresses only, size and time limits, rate-limited.
What this canonical checker does
Enter a page URL and the tool fetches it, records any redirects on the way, and inspects the canonical link tag and the HTTP Link header. It reports whether the canonical is absolute, whether the page declares exactly one, whether it points back at the page itself, whether it uses https, and whether the header and the tag disagree.
Why canonicals matter
The canonical tells search engines which address is the real one when the same content is reachable under several URLs, for example with and without a trailing slash or a tracking parameter. A canonical that points at the wrong page hands that page's ranking to another URL. A canonical that points at an http address on an https site, or at a page that redirects, sends conflicting signals and is quietly ignored.
Questions
Should every page have a canonical?
Yes, and on most pages it should point at the page itself. It costs nothing and prevents parameter and slash variants from splitting signals.
What is a self-referencing canonical?
A canonical whose URL is the page's own address. It is the normal case; the tool reports when it is missing.
Can a canonical point at another domain?
It can, for syndicated content. For everything else a cross-domain canonical is usually a mistake left over from a migration.
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