User datagram protocol is called connectionless because:

User Datagram Protocol (UDP) is called connectionless because it does not establish a dedicated end-to-end connection between the sender and receiver before data is sent. Unlike connection-oriented protocols, such as the Transmission Control Protocol (TCP), which establish a connection with various steps (like the three-way handshake in TCP) before any data is transferred, UDP simply sends packets (datagrams) directly to the recipient without ensuring the establishment of a reliable link. There’s no handshake, ongoing connection, or acknowledgment that the data received is correct or even that it’s been received at all. This approach minimizes overhead and can lead to faster data transmission, but it also means that delivery, arrival order, and data integrity are not guaranteed by UDP itself.