Canonical outside of head
This means that the URL in question has a canonical element specified in the HTML, but outside of the <head>.
Why is this important?
If a canonical is specified outside of the <head>, it will be completely ignored by search engines.
Ultimately this means that whatever you had hoped to accomplish with this rel=canonical will not come to fruition.
What does the Hint check?
This Hint will trigger for any internal URL which contains a canonical in the HTML, yet outside of the <head> area.
Examples that trigger this Hint:
Consider the URL: https://example.com/
The Hint would trigger for this URL if it had a canonical tag that was anywhere outside of the <head>, for example:
How do you resolve this issue?
This Hint is an 'Potential Issue', which means that it is unlikely to be affecting the site at the moment, but should be investigated as it could cause issues in the future.
If this Hint triggers, it indicates a configuration issue on the URL in question, which is likely due to an issue with a page template or plugin which is putting the canonical in the wrong place. The canonical tag will need to be removed from the <body> (and replaced in the <head>), so you may require developer assistance.