What does UDP stand for?
UDP stands for User Datagram Protocol. A connectionless transport protocol that sends datagrams without handshakes, acknowledgments or retransmission, so it is fast but unreliable. Used where speed matters more than every packet: DNS, DHCP, VoIP, streaming and TFTP.
UDP is the transport protocol for traffic where speed matters more than guaranteed delivery. There is no handshake, no acknowledgement and no retransmission: an application hands UDP a datagram and it is sent. The header is only 8 bytes. DNS queries, DHCP, voice and video calls, online games, NTP and SNMP use it. If reliability is needed, the application has to provide it. Because UDP has no connection, a NAT device or firewall keeps a short-lived entry for each exchange so that the reply can find its way back.
UDP in practice: an example
During a video call a few packets are lost. With UDP, the call goes on with a brief glitch in the picture. With a reliable transport, the picture would freeze while the lost data was sent again and would then arrive too late to be useful.
What UDP is confused with
UDP vs TCP: what is the difference?
UDP is connectionless and unreliable by design, with very little overhead. TCP is connection-oriented and reliable, with more overhead and delay. What TCP stands for
Which exams cover UDP?
UDP is on the official CompTIA acronym list for two of the four exams covered here.
- Network+ N10-009: 1.0 (Networking Concepts).
- A+ 220-1201 and 220-1202: 220-1201 2.0 (Networking).
Each number is a CompTIA exam objective and the name in brackets is its domain. The exam puts the term in a scenario; it does not ask you to recite the expansion.
Check yourself: two practice questions
Written by CertSprint for this page. They are not taken from any exam.
1. Which application is best suited to UDP?
- A live voice call
- A file transfer that must be complete
- An email delivery
- A database replication
Show the answer
A. A live voice call. In live voice a late packet is useless, so retransmission does not help. The other tasks need every byte to arrive.
2. Which feature does UDP lack compared with TCP?
- Port numbers
- A checksum
- Acknowledgement and retransmission of lost data
- The ability to cross routers
Show the answer
C. Acknowledgement and retransmission of lost data. UDP has ports and a checksum and is routed like any IP traffic. What it does not do is confirm delivery or resend.
Sources: RFC 768: User Datagram Protocol; RFC 1122: Requirements for Internet Hosts, Communication Layers. The acronym and its expansion come from CompTIA's official acronym lists, linked from each exam glossary above. The explanation, example and questions are CertSprint's own, checked against these sources on 11 November 2026.