Google’s John Mueller recently mentioned that while self-referencing canonical tags are not absolutely essential, they are beneficial.
Mueller stated: “It’s a great practice to have a self-referencing canonical but it’s not critical.”
This topic was discussed during a recent Google Webmaster Central hangout when a website owner inquired about the importance of using self-referencing canonicals.
Canonical tags are generally used to connect a non-canonical page to its canonical version, but they can also link a page to itself.
Self-referencing canonicals are advantageous because URLs may be linked with parameters and UTM tags.
In such cases, Google might identify the URL with parameters as the canonical version. A self-referencing canonical allows you to specify the URL you wish to be recognized as the canonical version.
Google suggests using self-referencing canonicals as a best practice, although they aren’t absolutely necessary for Google to identify the correct version of a URL.
Mueller’s complete response is available in the video below, starting at the 28:53 mark:
“It’s not critical to have a self-referencing canonical tag on a page, but it does make it easier for us to pick exactly the URL that you want to have chosen as canonical.
We use several factors to select a canonical URL, and the rel-canonical plays a part in that decision.
Particularly, elements like URL parameters, or if the URL is tagged in any specific manner – perhaps you have analytics tagging on links leading to that page – could cause us to choose the tagged URL as canonical.
With the rel-canonical, you’re indicating that you strongly prefer this specified URL as the canonical.
So it’s a great practice to have a self-referencing canonical but it’s not critical. It’s not mandatory, but it assists in ensuring the markup is correctly identified.”
