Alternatively, open up developer tools, go to the network panel, right-click on the headings and enable the protocol field. It will tell you which protocol was used for each request made by your browser. Obviously the server also needs to support HTTP/3 for a request to use HTTP/3.
Another user here commented that it's been enabled randomly for a subset of users. But not for me. And there's nothing on the web I've found about how to enable it. It was once on the Experimental menu, but no longer.
https://developer.apple.com/documentation/safari-release-not...
You can check with Cloudflare’s test page here:
https://cloudflare-quic.com
Alternatively, open up developer tools, go to the network panel, right-click on the headings and enable the protocol field. It will tell you which protocol was used for each request made by your browser. Obviously the server also needs to support HTTP/3 for a request to use HTTP/3.