Luke Mulks:

QUIC is enabled by default in Google’s Chrome browser and underlying Chromium open source browser code. As of March 2017, Chrome accounts for 58.9% of users browsing the web.
 Brave blocks QUIC requests. QUIC is an opt-in feature in Opera, and is currently not available in other Firefox, Edge, and Safari. HTTPS requests containing the alt-svc: quic=”:443″ response header fall back to traditional TCP connections in other browsers, or when QUIC fails in Chrome.