// the find
bagder/http3-explained
A document describing the HTTP/3 and QUIC protocols
A free book by Daniel Stenberg (the curl author) explaining HTTP/3 and QUIC from first principles — why TCP's head-of-line blocking problem necessitated QUIC, how the handshake works, 0-RTT, streams, and the current standardization status. It's aimed at developers who need to understand the protocol well enough to make deployment or implementation decisions, not just know that HTTP/3 exists.
Written by someone who actually shipped QUIC support in curl, so the tradeoffs and criticisms are grounded rather than promotional. The 'why' chapters (why not TCP, why QUIC over UDP, why TLS 1.3 mandatory) are better than most protocol docs at explaining motivation before mechanism. Available in 10+ languages with community translations that are reasonably well-maintained. The dedicated criticism chapter is rare in protocol documentation and worth reading — it covers ossification concerns and deployment friction honestly.
Last substantive update was mid-2024 and the QUIC ecosystem has moved — HTTP/3 prioritization (RFC 9218) and QUIC v2 (RFC 9369) are mentioned but coverage is thin compared to the core protocol chapters. The book stops at the protocol boundary: nothing about actually configuring nginx/Caddy/Envoy for HTTP/3, or what to expect from real-world performance measurements. No interactive examples or packet traces — for something as timing-sensitive as QUIC handshakes and 0-RTT, diagrams alone leave a lot on the table.