Rules / canonical rules

canonical.href.self

Default

warn

Plugin

canonical

The canonical href points at the page itself.

Why: A canonical link to another page asks search engines to show that page instead of this one. That is right for duplicates, such as print versions, but is often a template mistake that hides real pages. The rule needs the page URL, so it is skipped without a host.

URLs of one page match, with or without index.html or .html, because hosts serve about.html at /about too.

When off: canonical links to other pages pass.

<!-- On https://example.com/about/ -->

<!-- ✗ Fails -->
<link rel="canonical" href="https://example.com/" />

<!-- ✓ Passes -->
<link rel="canonical" href="https://example.com/about/" />

References

• Google: How to specify a canonical URL: Google recommends a self-referencing canonical link on each canonical page. Some pages are duplicates on purpose, so the rule warns.