What it is
An http canonical on an https page, or the reverse, points at the wrong version of the URL. After moving to https, every canonical should use https. HTTP canonical on an HTTPS page or vice versa. Splits consolidation across protocols.
Why does protocol mismatch in canonical matter for AI search?
Splits consolidation across protocols.
How do you fix it?
Canonicalise to HTTPS consistently.
How do you find it on your site?
- Check the protocol of each canonical against the page it sits on.
- Flag any http canonical on an https page.
- Update canonicals to https.
- Confirm the https version is the one that returns 200.
Which ranking and citation factors does it touch?
A protocol mismatch can canonicalise to a URL that redirects, undermining the consolidation and adding a hop.
What is the impact?
Medium. Direct.
What is the evidence?
Keep canonical protocol consistent (HTTPS). Google Search Central, Consolidate duplicate URLs (canonicalization); Google Search Central, Secure your site with HTTPS
Sources
Frequently asked questions about protocol mismatch in canonical
What does "Protocol mismatch in canonical" mean?
HTTP canonical on an HTTPS page or vice versa.
How do you fix protocol mismatch in canonical?
Canonicalise to HTTPS consistently.