User Datagram Protocol (UDP) is a lightweight transport layer protocol designed for fast, unguaranteed data transmission. Operating on top of IP, UDP transmits data immediately without establishing a connection or running a handshake beforehand.

Unlike TCP, UDP provides no packet numbering, no arrival confirmations, and no automatic retransmission for lost data. It follows a direct "send and forget" approach, sending packets with minimal overhead and no delay.

UDP is suited for scenarios where speed and timeliness matter more than perfection. In applications such as live video streaming, voice calls, and online games, a late-arriving packet is effectively useless because the moment it represents has passed. In such cases, skipping lost packets and continuing without interruption is preferable to stopping and waiting for retransmissions.