Make Sure A Separate PWA is Canonicalised to Your Mobile Site
Google won’t get confused between your main site and separate PWA as long as you have canonicalization in place.
Internal Linking Causes Google to Crawl Canonicalised Pages
Check your internal linking if you see Google crawling canonicalised pages.
Hreflang Should be Included Between the Canonical Versions of Pages
Including hreflang on paginated pages is fine but the most important thing is to include hreflang tags between the canonical versions of the page.
Parameter Handling Signals Are Stronger Than the Canonical Signal
Google won’t blindly follow URL parameter handling set in GSC, but John says that this is a stronger signal than using canonicals.
Pages With ‘Submitted URL Not Selected as Canonical’ Message in GSC Won’t be Indexed
If you see the ‘Submitted URL not Selected as Canonical’ message for a URL in Google Search Console, that means the page isn’t being indexed.
Use canonicalization Instead of Noindex for Duplicate Content
John recommends using rel=canonical instead of noindex in order to deal with duplicate content in the best way. This way the signals from both page versions can be combined rather than dropping all the signals from the noindexed page.
AMP Pages Need to Have Canonical Tags
AMP pages without a canonical tag run the risk of not being considered to be valid, as well as creating duplicate content issues.
Canonicalising to Redirects Can Increase Time Taken to Index Preferred Version
Canonicalising to redirects can increase the time taken for Google to decide which version to index, especially if these pages aren’t identical. Google also looks at other signals such as internal linking and sitemap files to make this decision.
Canonicalization For Filter Results Pages Isn’t Recommended
Canonicalization shouldn’t be used for filter pages. This is because canonical tags can be ignored and filter pages aren’t always the same as they have different types of results.