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Networkingbeginner
TCP vs UDP
Reliable ordered bytes, or independent datagrams with no delivery promise
Reviewed by Abhijith N M · 24 October 2026 · Editorial standards
The Simple VersionNo jargon
TCP opens a connection, numbers every byte, acknowledges what arrived, retries lost packets and delivers data in order. UDP sends independent datagrams with no handshake, ordering or retry. TCP is the default for HTTP, SSH and anything where missing bytes break the payload. UDP is for live video, games and telemetry, where a late packet is worse than a lost one. QUIC, the transport under HTTP/3, builds reliability and ordering in user space on top of UDP.
TCP vs UDP — Visual Breakdown
Option A
TCP (Transmission Control Protocol)
A
- ✓3-way handshake (SYN, SYN-ACK, ACK)
- ✓Guaranteed delivery
- ✓Packets arrive in order
- ✓Slower (overhead for acknowledgments)
- ✓Used by: HTTP, HTTPS, email, SSH
- ✓Good for: web apps, file transfers
Option B
UDP (User Datagram Protocol)
B
- ✓No handshake — fire and forget
- ✓No delivery guarantee
- ✓Packets may arrive out of order
- ✓Faster (no ACK overhead)
- ✓Used by: DNS, video calls, gaming, live streaming
- ✓Good for: real-time apps where speed > perfection
VS
Why It Matters in Production
Choosing UDP does not remove the need to handle loss, duplication and reordering; it moves that work into your application. That is a reasonable trade for real-time media, where you would rather drop a frame than stall the stream. For request/response APIs, TCP or QUIC is almost always the right base. Watch for head-of-line blocking on TCP when one lost packet delays everything behind it; that is one reason HTTP/3 moved to QUIC. Firewalls and NAT also treat UDP differently, which matters in corporate networks.
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