If you prefer the iOS or macOS Safari browser over Chrome or Chromium-based browsers, and you also use Google Docs or Gmail in the browser, you definitely want to enable this feature.
Click Safari menu → Preferences and choose the Advanced tab, enable “Show Develop in menu bar”:
Choose the Safari → Develop menu option and then “Experimental Features”:
Scroll down the list to find HTTP/3 and enable it like this:
Go to Settings > Safari > Advanced > Experimental Features > HTTP/3:
Now all Google QUIC functions are noticeably more responsive in Safari.