# TCP vs UDP
Confidence: high
Last verified: 2026-05-22
Generation: human_only


## TL;DR

TCP (Transmission Control Protocol) provides reliable, ordered, error-checked delivery — the 'guaranteed delivery' protocol. UDP (User Datagram Protocol) provides bare-bones, best-effort delivery — the 'fire and forget' protocol. TCP is for web pages, email, file transfers; UDP is for real-time (VoIP, gaming, streaming).

## Core Explanation

TCP features: three-way handshake (SYN→SYN-ACK→ACK), sequence numbers, acknowledgments, flow control (sliding window), congestion control. UDP features: no connection establishment, no ordering guarantee, no retransmission, 8-byte header. QUIC (HTTP/3) uses UDP to implement TCP-like reliability with better performance.

## Further Reading

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