For those who are unaware, “canonicalization” refers to the practice of making sure that for every instance of duplicate content on a site, one version is specified as the “preferred” or “source” URL to the search engines. Basically, you are telling Google, “Of all the URLs that contain this content, this is the URL that you should consider the authority. No other.”
When a proper audit identifying canonicalization issues is not performed, you can run into snags later when Google identifies your site as being a source of duplicate content, which can lead to algorithmic ranking losses, or even manual penalties.
Canonicalization issues generally occur when attempted canonicalization is not executed properly. Following are some common canonical issues that, once resolved, can result in rankings boosts to the site because of consolidated link equity.
Issue: Home page does not canonicalize properly
Many websites wind up with multiple versions of the home page that resolve on different URLs, such as:
When you have many different versions of the home page — all of which have inbound links pointing to them — this can cause canonicalization issues that will impact rankings.
In order to fix this, choose your preferred home page URL and 301 redirect all the other versions to it. For the www vs. non-www versions, take it a step further by specifying your preferred domain in Google Search Console.
Implementing redirects to the preferred version of the home page will consolidate your link equity, which can potentially enhance your search engine rankings.