Avoid conflicting canonicals
Multiple or conflicting canonical signals can make the preferred representative unclear.
Website + SEO
Check the page canonical signals.
Inspect the final URL, rel=canonical annotations, robots metadata and whether the canonical points back to the final page.
Result
Diagnostic result
Self-referential canonical
A self-canonical is a clear signal on the preferred page and is recommended by Google for canonical pages.
Do not canonicalize to fragments
URL fragments are generally not supported as canonical targets.
Canonical is a hint
Redirects, canonical annotations, sitemap inclusion and page similarity all contribute; a search engine may still select a different canonical.