Google's John Mueller confirmed that Googlebot is not yet crawling over HTTP/3 yet. He said if you do implement HTTP/3 for your site, it doesn't mean it won't benefit your users and thus possibly your core web vitals metrics. But Googlebot won't crawl over it yet.
This came up on Twitter where Michael Kohlfürst asked John Müeller (not sure I did that right...) if Google is crawling over HTTP/3. The truth is, Google just started crawling over HTTP/2 (if your site supports it) November 2020 and then in May 2021 said over half of crawling is now done over HTTP/2. So it is a bit early for HTTP/3 crawling, maybe?
HTTP/3 is the third and upcoming major version of the Hypertext Transfer Protocol used to exchange information on the World Wide Web, alongside HTTP/1.1 and HTTP/2. HTTP/3 runs over QUIC, which is published as RFC 9000. As of December 2021, the HTTP/3 protocol is still officially an Internet Draft, but is already supported by 73% of running web browsers, and according to W3Techs 24% of the top 10 million websites. It has been supported by Google Chrome (including Chrome for Android, and Microsoft Edge, which is based on it) since April 2020 and by Mozilla Firefox since May 2021. Safari 14 (on macOS Big Sur and iOS 14) has also implemented the protocol but support is hidden behind a feature flag.
Here are those tweets:
I don't think we crawl with http/3 but that doesn't mean you won't see positive effects for users (and with that, potentially indirectly core web vitals too).
— 🧀 John 🧀 (@JohnMu) December 6, 2021
There's always some risk, but it sounds like most of the big players (CDNs, servers, clients) are behind this, so I'm not too worried. It doesn't replace other connections, so even older devices will still work.
— 🧀 John 🧀 (@JohnMu) December 7, 2021
So yes, if users interact with your site in a more speedy and responsive manner, that may make your users happier and also may impact your CrUX data.
Forum discussion at Twitter.
