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Term

HTTP/2 and HTTP/3

Modern versions of the HTTP protocol that deliver parallel requests over a single connection (HTTP/2) or via the faster QUIC transport (HTTP/3).

HTTP/2 and HTTP/3 — explained in more detail

HTTP/2 (standardized in 2015) solved HTTP/1.1’s head-of-line blocking problem: many resources can run in parallel, binary-multiplexed over a single TCP connection. Headers are compressed (HPACK); server push was optional. HTTP/3 (2022, RFC 9114) replaces TCP with QUIC on UDP — connection setup needs only one roundtrip (instead of three), and connection migration between Wi-Fi and mobile works without a re-handshake.

For sites this means: shorter TTFB, less sensitivity to poor networks, no more need for domain sharding. Both are supported by all major CDNs and modern browsers.

Example / practical use

Cloudflare, Fastly and Bunny.net have HTTP/3 enabled by default — putting one of these services in front of your origin gets you the upgrade without server config. The browser’s DevTools network tab then shows “h3” as the protocol.

HTTP/2 runs on TCP+TLS, HTTP/3 on QUIC+UDP — the application API remains identical from a web developer’s perspective. TLS is independent: HTTP/2 is in practice always paired with TLS; HTTP/3 has TLS 1.3 baked into QUIC.

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