HTTP/3 Checker

HTTP/3 is the latest version of the HTTP protocol and is built on top of QUIC, a transport protocol designed to improve connection speed, reliability, and performance. The HTTP/3 Checker helps you verify whether a website supports HTTP/3 and QUIC by performing real protocol checks rather than relying on assumptions or server configuration alone.

The tool analyzes multiple signals, including HTTP/3 support, QUIC availability, Alt-Svc headers, DNS HTTPS records, and handshake results. This provides a more complete view of how a website advertises and delivers HTTP/3 connectivity.

Enabling HTTP/3 at the server or CDN level does not always guarantee that browsers can successfully use it. Configuration errors, missing DNS records, incorrect Alt-Svc headers, or handshake failures can prevent visitors from benefiting from HTTP/3 even when it appears to be enabled.

This tool is useful for developers, system administrators, hosting providers, and website owners who want to validate their HTTP/3 implementation. It helps identify whether HTTP/3 is properly advertised, whether QUIC connections can be established, and whether supporting infrastructure is configured correctly. Whether you're migrating to HTTP/3, troubleshooting connectivity issues, or validating a CDN configuration, the checker provides a quick way to confirm that everything is working as expected.