HTTP/1.1, HTTP/2, and HTTP/3

The major HTTP versions share semantics but use different wire protocols and transport behavior.

HTTP/1.1 is text-based and connection-oriented. HTTP/2 uses binary frames and multiplexed streams over TCP. HTTP/3 uses QUIC over UDP and avoids TCP head-of-line blocking between streams.

httpprotocolhttp1http2http3

Reference (http)

ALPN: h2
ALPN: h3

HTTP/1.1 is text-based and connection-oriented. HTTP/2 uses binary frames and multiplexed streams over TCP. HTTP/3 uses QUIC over UDP and avoids TCP head-of-line blocking between streams.

Common mistakes

Assuming a server can change HTTP semantics just because the connection uses HTTP/2 or HTTP/3.

Sources

MDN HTTP Reference