1 Answers
HTTP pipelining is a feature of HTTP/1.1 which allows multiple HTTP requests to be sent over a single TCP connection without waiting for the corresponding responses. HTTP/1.1 specification requires servers to respond to pipelined requests correctly, sending back non-pipelined but valid responses even if server does not support HTTP pipelining. Despite this requirement, many legacy HTTP/1.1 servers do not support pipelining correctly, forcing most HTTP clients to not use HTTP pipelining in practice.
The technique was superseded by multiplexing via HTTP/2, which is supported by most modern browsers.
In HTTP/3, the multiplexing is accomplished through the new underlying QUIC transport protocol, which replaces TCP. This further reduces loading time, as there is no head-of-line blocking anymore.