TCP vs UDP

TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) are the two main transport protocols on the internet. TCP is connection-oriented: it sets up a connection, numbers the data, resends anything lost and delivers it in order, so it is reliable but adds overhead.

UDP is connectionless: it sends packets without guarantees of delivery or order, which makes it faster with lower delay. TCP is used for web pages (HTTP/1.1 and HTTP/2), email and file transfer; UDP is used for video calls, online games, live streaming, DNS lookups and HTTP/3 (QUIC).