UDP

UDP is the bare-bones way to send data over the internet: you put a message in a packet, called a datagram, address it and send it, with no connection set up first. There are no acknowledgements, no retries and no ordering, so a datagram might arrive late, out of order, twice or not at all, and UDP won’t tell you. That sounds worse than TCP, but it means no waiting: a video call or online game would rather skip a lost frame than freeze while it’s resent. DNS uses it for quick one-shot questions, and QUIC, the transport under HTTP/3, builds its own reliability on top of UDP.