If you’re using Google’s Search Console (which you should be), it will regularly check your website for indexing errors that can affect your placement on Google and other search engines. One of these errors is “Duplicate without user-selected canonical.” This means that Google found duplicate URL’s that aren’t “canonicalized.” A canonical URL is the preferred version of a web page. When a canonical URL isn’t specified for what Google determines is duplicate content, it will assign one on its own, and won’t index the duplicate pages.
How do you fix it?
Before attempting to fix this error, you should first decide whether these pages should even exist on your website. If not, simply remove them and return an HTTP 410 status, which will tell search engines that the page has been removed permanently.
If, however, the pages serve a purpose on your site, you should then decide if you want them to be indexed by Google. If you do, you should specify a canonical URL in the page header, for example:
<link rel="canonical" href="https://www.website.com/page/" />
You can see which URL Google thinks is most relevant by using their URL Inspection tool.
If the pages contain content you’d rather not be indexed, such as an account login page, you can tell search engines this using a “noindex” directive, such as:
<meta name="robots" content="noindex" />
Once you’ve done one of the above, you can request that Google validate your changes in the Search Console.
If you need further guidance on this or any other Search Console issue, feel free to reach out!