Quick answer
A canonical should normally point to the preferred URL on the same site origin. NOTABIS reports canonical-off-origin when the first measured canonical resolves to a different origin from the audited site. Cross-origin canonicals can be deliberate, but confirm ownership, content equivalence, and the reason for consolidation before keeping one.
What the issue means
Origin includes scheme, host, and port. These are different origins:
https://example.com/page
https://cdn.example.net/page
A subdomain can be a separate origin even when it belongs to the same organisation. A relative canonical inherits the page’s origin and is not off-origin by itself.
Why it matters for SEO
Canonical signals influence which URL a search engine treats as the representative of duplicate or similar content. An unintended off-origin target can consolidate signals away from the site or point to a page with different content. Google may ignore a canonical that conflicts with stronger evidence; the finding is a review, not a guaranteed ranking loss.
How NOTABIS detects it
The canonical-off-origin rule resolves the first link[rel="canonical"] against the page URL, then compares the result with the audit origin. It records a page-level issue when the resolved URL is not same-origin. It does not verify ownership, content equivalence, response status, or whether a cross-origin relationship is intentional.
How to check it yourself
Inspect the raw canonical value, resolve it, and compare scheme, host, and port with the audited site. Request the target and compare its content, redirects, robots directives, and indexability. Check whether a CDN hostname is only an asset host or is intentionally the canonical publishing host.
How to fix it
For ordinary site pages, emit a same-origin canonical that matches the final preferred URL. Correct host, scheme, port, and trailing-slash rules in the generator, then remove duplicate tags. If content is intentionally syndicated or hosted across related origins, document the relationship and verify that the target is the exact representative you want indexed.
<link rel="canonical" href="https://example.com/page">
Align internal links, redirects, and sitemaps with the chosen host and recheck the public response after deployment.
When this is intentional or does not need fixing
Cross-origin canonicalisation can be appropriate for syndicated content or a site migration when the target is controlled and equivalent. A CDN URL used only for assets is not a page canonical. Do not rewrite a deliberate multi-site strategy without checking ownership and contracts.
Related issues
Read canonical URL present, multiple canonical tags, canonical and redirects, and missing canonical URLs.
Run a NOTABIS audit
NOTABIS resolves the measured canonical and shows when it points away from the audited origin, so you can verify whether the relationship is deliberate.