Statistics

What the publicly checked domains reveal about HTTP/3 adoption.

Promised but not delivered

Of 411 domains with recorded Alt-Svc data, 241 advertise HTTP/3 and 28 of those no QUIC connection could actually be established.

That combination is the most common real-world failure, and it is almost always a firewall dropping UDP/443 – the server config is fine, the packets never arrive. How to fix it

Server and CDN

Only checks run since 30 July 2026 carry server data, so this table is still small and not representative.

Over time

Basis: only domains whose check was explicitly shared publicly. This is a self-selected sample of visitors to this site, not a representative survey of the web.

← Back to the HTTP/3 check