One protocol says:
“Wait… did it reach safely?”
The other says:
“I sent it. Not my problem.”
That’s TCP vs UDP in one sentence.
In this blog, we’ll break down TCP and UDP, understand their differences, and finally see where HTTP fits in — and why it chooses a side.
Topics We’ll Cover
- What are TCP and UDP? (high level)
- Key differences between TCP and UDP
- When to use TCP
- When to use UDP
- What is HTTP and where it fits
- Relationship between HTTP and TCP
TCP and UDP
TCP — Transmission Control Protocol
TCP is a reliable, connection-oriented network protocol.
What TCP does:
- Transfers data from your device to a server over the internet
- Establishes a connection using a 3-way handshake
- Ensures data reaches the destination without loss or corruption
- Maintains the correct order of packets
- Retransmits lost packets if needed
Because of all these checks, TCP is slower than UDP, but it’s extremely reliable.
Examples where TCP is used:
- Chat applications
- Messaging apps
- Emails
- File downloads
- Web browsing (HTTP/HTTPS)
UDP — User Datagram Protocol
UDP is a fast, connectionless network protocol.
What UDP does:
- Transfers data over the internet without establishing a connection
- Sends packets without checking if they arrive
- Does not care about missing or out-of-order packets
- Does not retransmit lost data
This makes UDP much faster, but less reliable.
Examples where UDP is used:
- Video calls
- Live streaming
- Online gaming
- Voice calls
Ever noticed glitches or buffering during a video call?
Yep — that’s UDP in action 😉
It prefers speed over perfection.
Key Differences Between TCP and UDP
| TCP | UDP |
|---|---|
| Connection-oriented | Connectionless |
| Uses 3-way handshake | No handshake |
| Reliable (guarantees delivery) | Less reliable |
| Maintains packet order | Packets may arrive out of order |
| Slower | Faster |
| Error checking & retransmission | No retransmission |
| Used in chats, emails, downloads | Used in streaming, gaming, calls |
When to Use TCP?
👉 Use TCP when:
- Data accuracy matters more than speed
- Losing data is not acceptable
- Order of data is important
Examples:
- Sending an important email
- Downloading a file
- Chatting or messaging
You can tolerate a bit of delay, but you cannot tolerate corrupted data.
When to Use UDP?
👉 Use UDP when:
- Speed matters more than perfection
- Small data loss is acceptable
- Real-time communication is needed
Examples:
- Video calls
- Live streaming
- Online gaming
If a few packets are lost, it’s better to move forward than wait and retransmit.
How Does the Browser Use These Protocols?
Now the big question 👇
How does your browser load a website using these protocols?
That’s where HTTP comes in.
What is HTTP and Where It Fits?
HTTP — HyperText Transfer Protocol
HTTP defines:
- What data is requested
- What data is sent back
It does not decide how data is delivered safely.
Example: Opening Facebook
- You type:
www.facebook.com
- The browser sends an HTTP request:
GET / HTTP/1.1
Host: www.facebook.com
- The server processes the request:
- Which page is requested?
- Are you logged in or not?
- The server sends an HTTP response:
HTTP/1.1 200 OK
Content-Type: text/html
That’s how a web page loads 🙂
TCP vs UDP vs HTTP — Who Does What?
- TCP / UDP → Decide how data is transferred
- HTTP → Decides what data to request and send
So where does HTTP sit?
👉 HTTP sits on top of TCP and uses it to deliver web data reliably.
Relationship Between HTTP and TCP
HTTP only defines the rules of communication.
It doesn’t handle:
- Reliability
- Ordering
- Retransmission
That’s where TCP comes in.
TCP:
- Creates a reliable connection
- Sends data in the correct order
- Retransmits lost packets
In simple words:
- HTTP talks
- TCP makes sure the message is delivered properly
That’s why traditional HTTP chooses TCP over UDP.
Final Conclusion
- TCP → Reliable, ordered, slower
- UDP → Fast, unordered, less reliable
- HTTP → Needs reliability → chooses TCP
Speed is important, but for the web, correct data matters more.
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