Here is the specific question that was submitted:
“You can indicate your preference to Google using these techniques, but Google may choose a different page as canonical than you do, for various reasons. So, what are the reasons? Thanks!”
In response, Mueller says its common for websites to have multiple, unique URLs that lead to the same content. For example, there’s WWW and non-WWW versions of a URL.
Another common configuration is when the homepage is accessible as index.html, or when upper and lowercase characters in URLs lead to the same pages.
Ideally there should not be any alternate versions of URLs, but that rarely happens. So Google chooses canonical URLs to display in search results based on two general guidelines:
- Which URL does it look like the site wants Google to use?
- Which version of the URL would be most useful to searchers?
Site owners can indicate their preferred canonical URLs to Google by following the guidelines in the next section.
How to Tell Google Which Canonical URL You Prefer
Site owners can send signals telling Google which URL they prefer. The more consistent the signals are, the more likely Google will choose the site’s preferred URL.
Those signals are as follows:
- Link rel canonical annotation that matches throughout the site
- Internal linking using the preferred URL format
- Preferred URLs in the sitemap file
Mueller adds that Google has a preference for HTTPS URLs over HTTP URLs, and also tends to choose “nicer-looking” URLs as canonical.
The key takeaway here is, if you have a strong preference regarding which version of a URL gets chosen in search results then make sure to use it consistently.
The more consistent the site is, the more likely Google will use the site’s preferred canonical URL.
What Happens if Google Chooses a Different URL?
A preferred URL is just that – a preference. Mueller says there is no negative impact on rankings if Google chooses a different canonical URL than what you would prefer to have chosen. It’s also fine to have no preference at all.
When it comes to canonical URLs, consistency is key. But don’t lose sleep if you put all the right signals in place and Google still chooses a different version of the URL as canonical.