Glossary

HTTP/3 and QUIC

HTTP/3 is the third major version of HTTP, using QUIC (over UDP) instead of TCP. It solves the fundamental HTTP/2 problem: head-of-line blocking at the transport layer. Supported by most browsers and CDNs.

Why QUIC instead of TCP

HTTP/2 multiplexes requests over a single TCP connection. But TCP guarantees order: losing one packet blocks all subsequent ones. QUIC — over UDP — isolates streams: a lost packet blocks only one stream; the rest continue.

HTTP/3 benefits

0-RTT connection — reconnecting to a known server without an extra handshake
Built-in TLS 1.3 — encryption is part of the protocol, not a separate layer
Better on mobile — QUIC handles IP changes correctly (roaming)

Support

Cloudflare, Google, Facebook, Chrome, Firefox — all support HTTP/3. Nginx requires quiche or a custom build. For most applications — transparent through a CDN.