HTTP/1.1, 2, and 3

Start with the idea

HTTP/1.1 can reuse connections, but response ordering and limited pipelining often led browsers to open multiple connections. HTTP/2 multiplexes streams over one TCP connection, which removes application-level blocking but not TCP's — one lost packet still stalls every stream. HTTP/3 moves onto QUIC over UDP, so loss recovery can proceed independently per affected stream; congestion control still applies to the connection. Its handshake integrates TLS.

HTTP/1.1 can reuse connections, but responses on a connection are generally constrained by request ordering in common deployments. Pipelining exists in the protocol but saw limited browser use; clients often opened several connections to avoid waiting behind one slow response. HTTP/2 multiplexes streams over one TCP connection and compresses headers, improving concurrent request handling. Because all streams still share that TCP connection, packet loss can cause transport-level head-of-line blocking even when the HTTP streams are logically separate.