Last month Google told us that beginning in November GoogleBot will support crawling sites over HTTP/2. Well, that time has come and if you see that happening, it is because Google thinks can save computing resources for your site crawling that way.
In fact, Google just updated its Googlebot documentation to make sure it is properly documented. What was added were these two paragraphs:
Generally, Googlebot crawls over HTTP/1.1. However, starting November 2020, Googlebot may crawl sites that may benefit from it over HTTP/2 if it’s supported by the site. This may save computing resources (for example, CPU, RAM) for the site and Googlebot, but otherwise it doesn’t affect indexing or ranking of your site.
To opt out from crawling over HTTP/2, instruct the server that’s hosting your site to respond with a 421 HTTP status code when Googlebot attempts to crawl your site over HTTP/2. If that’s not feasible, you can send a message to the Googlebot team (however this solution is temporary).
You can read more about this change in my original story.
Forum discussion at Twitter.