ERR_QUIC_TIMEOUT — QUIC session did not complete handshake or idle timeout exceeded. Causes: significant packet loss (>5% UDP drop), slow network (<1 Mbps), middlebox reset of long-idle connections, mobile network UDP filtering. Fallback to HTTP/2 starts after 10s by default. Fix: reduce server idle_timeout or disable HTTP/3 on flaky networks.
Below: causes, fixes, FAQ.
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quic_retry on; ssl_session_timeout 10m;Protocol testing checks which TLS versions the server supports. Legacy versions (TLS 1.0, SSL 3.0) have known vulnerabilities and must be disabled.
Check TLS 1.0, 1.1, 1.2, 1.3 support — with security rating for each.
List of supported cipher algorithms with strength rating for each.
ALPN negotiation check for HTTP/2 (h2) and HTTP/3 (h3) via QUIC.
Detection of BEAST, POODLE, DROWN, and other TLS/SSL attacks.
TLS configuration check
protocol and cipher audit
HTTP/2 compatibility
HTTPS ranking signal
SSL monitor alerts 30 days before expiry and on TLS version changes.
Sign up freeParadox: QUIC designed for fast handshake (0-RTT), but on packet loss UDP retransmission is manual (vs TCP kernel). At 5% loss QUIC ~= TCP. >10% — TCP wins.
nginx 1.25+ with QUIC: quic_gso on; quic_retry on; for better performance.
Cloudflare Analytics shows HTTP/3 share. Typical 2026: 15-30% desktop, 5-15% mobile.
Enterno HTTP checker tests standard HTTP. For QUIC — specialized testing (h3i, curl --http3).
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