During the September 9 edition of #AskGoogleWebmasters , John Mueller said that Google might select a canonical URL based on your site’s perceived preference and the URL that is more useful for the user.
Here is the question:
“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!” user @uale75 asked via Twitter.
Mueller contextualized the question by providing some examples of common configurations where multiple unique URLs lead to the same content, such as when the homepage is accessible as index.html or when both lower and uppercase versions of a URL direct to the same page.
“For search, it doesn’t make much sense to index and show all of these versions, so we try to pick one and focus on that,” Mueller explained. “We try to pick the canonical URL by following two general guidelines: First, which URL does it look like the site want us to use; so, what’s the site’s preference? And secondly, which URL would be more useful for the user?”
Mueller said that, in terms of the “site’s preference,” Google will take into a number of factors into account, such as:
- Link rel canonical annotation.
- Internal linking.
- The URL in the sitemap file.
- HTTPS URLs over HTTP URLs.
- The “nicer-looking” URL.
“For all these, we consider the factors involved for each potential canonical URL and then pick the one where more things come together.”
“If you’re a site owner and you have a strong preference regarding URLs that you want to have shown to users in search, first of all, you should make sure that you use those preferences consistently across your website,” he advised. “Ideally, search engines wouldn’t even be able to stumble across any of those alternatives — if you have a preference, then stick to it.”
But what happens if another URL is chosen?
“Simply put, it’s just the URL that’s shown in search. If our systems pick a different URL as a canonical, it’ll rank just the same in search. In the end, it really just comes down to your preference,” Mueller stated, adding, “If a different URL happens to be chosen from time to time, that’s not going to negatively affect the site either.”