TCP vs UDP: What’s the Difference?

TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) are the two most common ways of transporting data across the modern web. You might not know it, but you use them both just about every day.

Read on to find out how!

Why Can’t the Server Just Send All My Data At Once?

When you visit a website, or view a live stream, it might seem like you’re getting all your data simultaneously. In reality, this couldn’t be further from the truth. The internet doesn’t work like that– and there’s a good reason for it.

To avoid overwhelming our networks, our data gets broken into chunks. Imagine you have a 500mbps connection, and you’re downloading a 100GB video game. Without chunking, your router would fail to process the data and your network would slow to a crawl–effectively crashing it!

Different protocols like TCP and UDP are used to define how these chunks are transmitted.

• TCP: Chunks are sent and verified in succession. Think of this almost like mail correspondence. Your machine receives a letter, reads it, and then asks for the next one.
• UDP: All chunks are sent in rapid-fire–like a .50 caliber data turret!

Transmission Control Protocol

TCP is at the heart of all your HTTP/HTTPS requests. TCP cares about all the details of our connection. With TCP, we initiate a handshake and then our response comes back in order. Every time our client receives a response, it sends an ACK (acknowledgement) to the server. This way, the server always knows the state of the information it delivered.

Let’s pretend you’re downloading a file over TCP and it gets split into 4 chunks, or segments. The server sends our first chunk, and our HTTP client tells it everything went OK. Then, we repeat that process with chunks 2, 3 and 4. We suggest you learn more about making HTTP requests.

Core Functionality

Here’s the step by step of how TCP works.

1. The Client (your smartphone) initiates a handshake and requests your email history from the server.
2. The history is too large to send all at once, so it splits your history into chunks (with TCP, these chunks are called segments).
3. The server sends the first chunk.
4. Your phone sends an ACK (acknowledgement) that the first chunk was received.
5. The server sends the second chunk.
6. Your phone sends another ACK.

This process repeats on a loop until all of the data has been transferred.

Applications

Wherever data needs to be accurate, TCP is there running things under the hood. You use TCP in all the following applications.

• Web Browsing: HTTP/HTTPS (HyperText Transfer Protocol)/(HyperText Transfer Protocol Secure) uses TCP to send pages to your browser.
• Email: SMTP (Simple Mail Transfer Protocol), IMAP (Internet Message Access Protocol), and POP3 (Post Office Protocol version 3) all use TCP to ensure that your messages arrive in order–not random, jumbled gibberish.
• Large File Downloads: FTP (File Transfer Protocol) and SFTP (Secure File Transfer Protocol) ensure that large downloads occur in an orderly fashion without corrupting your data.

Pros and Cons

Pros

• ✅ Reliable: TCP ensures that all data gets delivered.
• ✅ Error-free: If a chunk gets sent or processed incorrectly, TCP makes sure to retransmit the data.

Cons

• ❌ Slow: Due to its strict accuracy rules, TCP is often slow.
• ❌ Network Congestion: In heavy traffic, TCP gets bogged down while waiting for everything to align perfectly.

User Datagram Protocol

UDP is kind of like TCP’s laidback cousin. TCP is all about handshakes and maintaining a connection until the data arrives perfectly. Our UDP chunks are technically called datagrams. With UDP, we send a single request and the server sends all the chunks in rapid succession without verifying their accuracy.

When processing responses, there is no ACK system or handshake. Your machine sends a single request and receives its data. The server hears this request and responds by firing off all of these chunks with no particular order.

Core Functionality

The process in UDP is much more fast and loose.

1. Your machine requests the data
2. The server sends each chunk in rapid-fire with no verification or ACKs.

Your data arrives as fast as possible and usually out of order. The server doesn’t care about missing chunks or data integrity.

Applications

• Live Streaming: When you watch a YouTube livestream, the app on your phone or TV sends the requests and opens up the stream. Then the data starts flying!
• Online Games: With modern online games, we deal with KB (kilobytes) and sometimes even MB (megabytes) in just a few seconds. UDP gets the game rendered on your screen with minimal latency.
• DNS (Domain Name System) Lookups: When you came here to the Bright Data Blog, a DNS server used UDP shoot the IP address right into your browser.

Pros and Cons

Pros

• ✅ Blazing fast: UDP doesn’t care about accuracy, it’s like a machine gun firing off all its data as fast as possible.
• ✅ Lean: There are no resources wasted on handshakes and ACKs–just all the data coming as fast as possible.

Cons

• ❌ Unreliable: Data can arrive jumbled or sometimes not at all.
• ❌ Hands-off: UDP servers don’t care that your livestream isn’t working. They just keep sending more data.

Common Misconceptions

Misconception #1: TCP is Always Slower Than UDP

Yes, TCP adds a delay through handshakes and ACKs. However, modern protocols like TCP Fast Open (TFO) and Multipath TCP (MPTCP) are reducing TCP latency and improving performance. While UDP is almost always faster, fine-tuned TCP can sometimes outperform even UDP.

Misconception #2: UDP is Only for Streaming & Gaming

Real-time applications are the primary niche for UDP, however this isn’t just limited to live streams and online gaming. Low-latency trading, sensor technologies and even DNS can utilize UDP.

Misconception #3: You Can Only Use One

Modern technologies actually utilize both TCP and UDP. When you watch TV through Hulu or YouTube, your actual setup like initial connection, metadata, and buffering are often sent using TCP. While streaming this content, UDP is often used for adaptive bitrate and reduced lag during the stream.

When To Use Each One

Conclusion: Choose The Right Tool For The Right Job

Both TCP and UDP play a crucial role in how data moves across the internet. TCP ensures reliability and accuracy, making it ideal for web browsing, emails, and file transfers. On the other hand, UDP prioritizes speed, making it the go-to choice for live streaming, online gaming, and real-time communications.

When it comes to proxies, the right protocol can make all the difference. If you need stable, reliable connections for web scraping, data collection, or secure browsing, HTTP/HTTPS proxies using TCP are your best bet. But if speed and low latency are your priority, such as for streaming or gaming, SOCKS5 proxies with UDP support can provide the performance you need.

Take a look at the selection of proxy services below:

• Residential Proxies: Access the web through a real consumer device on a home internet connection.
• Datacenter Proxies: Route your requests some of the best hardware and bandwidth available in modern datacenters.
• Mobile Proxies: Similar to residential, but your request is going through a mobile device on a cellular data network.
• ISP Proxies: Run your traffic through a specific internet service provider.
• Web Unlocker: Automatically connect to the best available proxy for your target site. No CAPTCHAs, no hassle.

Sign up for a free trial and get started today!