TCP is reliable (guarantees delivery). UDP is fast (no delivery guarantee). Use TCP for file transfers, UDP for gaming/streaming.
Factor
TCP
UDP
Reliability
✅ Guaranteed delivery
❌ No guarantee
Speed
❌ Slower
✅ Faster
Use Cases
File transfer, web, email
Gaming, VoIP, streaming
Overhead
❌ Higher
✅ Lower
TCP
Transmission Control Protocol — reliable, ordered delivery.
✓ Pros
Guarantees packet delivery
Maintains packet order
Error checking
Automatic retransmission
✗ Cons
Slower due to overhead
Higher latency
Requires connection setup
UDP
User Datagram Protocol — fast, unreliable delivery.
✓ Pros
Much faster
Lower latency
No connection setup
Less overhead
✗ Cons
No delivery guarantee
No error checking
Packets can arrive out of order
Packets can be lost
The Verdict
Use TCP when data must arrive intact (downloading files, loading websites). Use UDP when speed matters more than perfection (online gaming, video calls, live streaming).
Frequently Asked Questions
Why do games use UDP instead of TCP?
Games need low latency. It's better to miss a packet (skip one frame) than wait for it to retransmit (lag).
Can I choose TCP or UDP?
No. The application chooses. You can't manually select which protocol to use.
Which is more secure?
Neither. Security is handled by other protocols (SSL/TLS). Both TCP and UDP can be encrypted.