Anything Contained on Non-canonical Pages Will Not Be Used for Indexing Purposes
When Google pick a canonical for a page, they will understand there is a set of pages, but only focus on the content and links of the canonical page. Anything that is only contained on the non-canonical versions will not be used for indexing purposes. If you have content on those pages that you would like to be indexed, John recommends ensuring they are different.
Review Canonical Signals if Google Are Continually Picking a Different Canonical to the Ones Set
Google may occasionally pick a canonical that is different the one that has been set for certain pages, but this doesn’t change anything from a ranking point of view. However, if you’re seeing this on a large scale, John recommends reviewing if you are sending confusing signals to Google.
No Need to Remove Internal Links on Non Canonical Pages as Google is Able to Figure Out Connections
Google sees links from a canonical page to a canonicalised page, and sometimes there can be multiple internal links that are associated with each. In this case, Google will combine all of the signals and keep them with each page, but is able to understand the connection between the canonical and canonicalised pages.
Google Will Usually Drop Session IDs from URLs
Instead of choosing a representative URL for a set of URLs with session IDs, Google will usually drop the session ID from the URLs completely if it recognises that they don’t return any unique content.
Google Would View a Page Canonicalized to a Noindex URL as a Noindexed Page
If you have a canonical link pointing to a page that is noindexed, the page canonicalised to it would also be considered noindex. This is because Google would view it as a redirect to a noindex page and therefore drop it.
There is No Risk of a Noindex Signal Being Transferred to the Target Canonical Page
If a page is marked as noindex and also has a canonical link to an indexable page, there is no risk of the noindex signal being transferred to the target canonical page.
Having Canonical Tags Set For Parameter URLs Helps Google Understand Connections Between Pages
Google tries to figure out the canonical URL for parameter pages that are included in the GSC parameter handling tool, so they may crawl these pages to identify and understand the canonical set up and connection.
Canonical Tags Should Remain The Same Between Desktop & Mobile Sites Even With Mobile First Indexing
If you have a separate m. version of your site, the canonical should remain pointing to the desktop version, despite mobile-first indexing. This is because Google will use the canonical tag to understand which of the pages belong together. Internally, Google will pick the mobile version as canonical.