HTTP/3
HTTP-over-QUIC — RFC 9114 (2022). QUIC is encrypted transport over UDP port 443. Eliminates TCP head-of-line blocking, faster handshake (0-RTT possible). ~30% of modern HTTPS traffic 2024.
Discovery: server announces HTTP/3 support via the Alt-Svc header on an HTTP/2 response, client switches for subsequent requests. Cloudflare, Facebook, Google fully deployed. Nginx: HTTP/3 support since 1.25 (2023). Browser support: Chrome, Firefox, Safari default-enabled. Performance gain varies: 5-30% improvement on lossy-mobile networks, less on stable fiber. UDP-blocking issues: corporate firewalls often block UDP-443, fall-back-to-TCP H2. Standard for modern web serving.