UDP: definition, explanation, and why it matters

Definition

User Datagram Protocol — a lightweight, connectionless transport protocol used where low latency matters more than guaranteed delivery, including games, voice, video, and DNS.

Plain-English explanation

UDP sends datagrams without setup or retransmission. If a packet is lost, the application decides what to do — drop it, interpolate, or request resend.

This minimal overhead makes UDP ideal for real-time media (VoIP, video calls), online games, and protocols like DNS where a single small request and response are all that's needed.

Real-world examples

• WebRTC video calls send audio and video frames over UDP because a missing frame is preferable to a frozen call.
• QUIC (and therefore HTTP/3) runs over UDP and rebuilds reliability features in user space for better performance.

Why it matters

UDP's behavior explains why some networks (corporate firewalls, hotel Wi-Fi) break games and calls but allow web browsing — they often block or rate-limit UDP.

Common misconceptions

• Myth: UDP is faster than TCP.
  Reality: Per-byte, they travel the same. UDP simply skips the setup and recovery that TCP performs, which is faster only in scenarios where that recovery isn't needed.

Frequently asked questions

Why do online games use UDP?

Game state updates need to be timely. A late update is useless, so retransmission would just add lag without value.