Canonical consistency

What this check looks for

Given a page with at least one canonical link, this check fails if more than one canonical tag is present (crawlers may ignore all of them when that happens), and fails if the single tag's href is missing or doesn't resolve to a valid absolute URL. If the canonical resolves to the same URL as the page itself, it passes as self-referencing. If it resolves to a different host entirely, it fails, since cross-host canonicals de-index the page you're looking at. If it points elsewhere on the same host, it warns, prompting you to confirm the consolidation is intentional. Pages with no canonical at all report "na" here — that's covered by meta.canonical.presence.

Why it matters

Multiple or malformed canonical tags leave search engines to pick one arbitrarily or discard the signal entirely, which reopens exactly the duplicate-content ambiguity canonicals are meant to close. A cross-host canonical is a strong instruction to index a different domain instead of this one — sometimes intentional (syndicated content), but often a copy-paste bug that silently removes a page from your own site's search presence. AI crawlers follow the same signal, so a broken canonical can misdirect which domain gets credited as the source in an AI-generated answer.

How to fix it

Keep exactly one canonical link, pointing at an absolute, valid URL:

<!-- Broken: two canonicals, one malformed -->
<link rel="canonical" href="/headphones/wireless-nc">
<link rel="canonical" href="https://www.acme.com/headphones/wireless-nc?utm_source=ad">

<!-- Fixed: one canonical, absolute, parameter-free -->
<link rel="canonical" href="https://www.acme.com/headphones/wireless-nc">

If a warn or fail surfaces a cross-host or cross-URL canonical you didn't intend, remove the extra tag or correct the href to reference this page.