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QUIC Checker

Probe a host for QUIC: which versions it supports, and a full handshake with the negotiated cipher and certificate.
HTTP/3 Checker Real HTTP/3 over QUIC — handshake and request Port Checker Check TCP and UDP ports of any host at once Proxy Checker Every protocol in one check — one proxy or 20,000 Website Checker Is it up? From here and around the world

Version negotiation

We ask the server which QUIC versions it speaks and list them, then complete a handshake with a compatible one — reporting QUIC v1, v2, drafts and vendor versions.

More than HTTP/3

QUIC carries HTTP/3, DNS-over-QUIC and more. Point this tool at port 443 for h3 or 853 for DoQ and it adapts the ALPN accordingly.

Handshake details

For every QUIC endpoint you see the negotiated version, the TLS cipher, the ALPN protocol and the certificate, plus how long the handshake took.

Frequently asked questions

What is QUIC?

QUIC is a modern transport protocol that runs over UDP with built-in TLS 1.3. It powers HTTP/3 and reduces connection setup time.

Why does QUIC fail when HTTPS works?

QUIC needs UDP on port 443. Firewalls and some networks block UDP, in which case browsers silently fall back to TCP.

What is DoQ?

DoQ is DNS over QUIC (RFC 9250), an encrypted DNS transport that usually listens on UDP port 853. Enter the resolver as host:853, for example dns.adguard-dns.com:853, and the checker switches to the DoQ protocol.

Which QUIC versions exist?

QUIC version 1 (RFC 9000) is the standard used by HTTP/3. Version 2 (RFC 9369) and older draft versions still exist; the checker shows which of them a server accepts.