HTTP/2 and HTTP/3 (QUIC) Test

Check whether a website supports the modern web protocols: HTTP/2 negotiated in the TLS handshake, HTTP/3 over QUIC advertised in Alt-Svc, and TLS 1.3.

How it works

HTTP/2, HTTP/3 and QUIC

HTTP/2

Many requests over one connection, with header compression. Browsers use it when the server offers h2 during the TLS handshake (ALPN).

HTTP/3 and QUIC

HTTP/3 runs over QUIC on UDP, avoiding head-of-line blocking and connecting faster on mobile networks. Servers announce it with an Alt-Svc header.

FAQ

Frequently asked questions

Why does my server not offer HTTP/3?

It needs a QUIC-capable server or CDN and UDP port 443 open in the firewall.

Does HTTP/3 replace HTTP/2?

No. Browsers fall back to HTTP/2 when UDP is blocked, so keep both enabled.

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HTTP/3 on by default with Yeap CDN

Global acceleration with HTTP/3

CDN