TCP vs UDP Tests
Why we run both tests, what each one reveals, and how to pick the right test for your situation.
Overview
Most speed tests only measure TCP — the protocol used by web browsers and downloads. That gives you an incomplete picture. TCP is designed to hide network problems by automatically retrying lost data. A network can be quietly dropping 5% of packets while your TCP speed test shows perfectly normal results.
That's why NetworkTests.com runs both. TCP tests show how fast your connection handles reliable traffic. UDP tests reveal the true quality of your connection — packet loss, jitter, and latency that TCP would normally paper over.
TCP Tests
HTTPS · TCPTCP (Transmission Control Protocol) guarantees delivery. If a packet is lost on the way, TCP automatically detects it and resends it. Your data always arrives complete and in order — it just might take longer than expected.
Our TCP test measures the full connection setup time to well-known cloud providers — Google, Cloudflare, Amazon, and Microsoft. This captures what your browser experiences when loading a real website: DNS resolution, TCP handshake, TLS encryption setup, and the first response.
What TCP Tests Measure
DNS Resolution Time
How long it takes to look up the server's IP address. Slow DNS adds delay to every new connection.
TCP Handshake Duration
The time for the initial back-and-forth to establish a connection. Reflects raw network latency.
TLS Negotiation Time
Time to agree on encryption keys. Usually the largest portion of connection setup.
Total Round-Trip Latency
End-to-end time from request to first byte of response — what your browser actually waits for.
TCP results may look good even when your network has problems. Because TCP retransmits lost packets silently, high packet loss shows up as increased latency rather than visible errors. If your TCP latency is elevated but not obviously broken, run the UDP test to see the real picture.
UDP Tests
WebRTC DataChannel · UDP-likeUDP (User Datagram Protocol) prioritizes speed over reliability. Packets are fired off and forgotten — there are no retransmissions, no reordering, no built-in error recovery. If a packet is lost, it's gone.
This makes UDP the protocol of choice for real-time applications: video calls, online gaming, VoIP, and live streaming. These apps cannot afford to wait for retransmissions — a retransmitted video frame would arrive too late to be useful. They'd rather have a brief glitch than a noticeable delay.
We use WebRTC DataChannels configured for unreliable and unordered delivery to emulate true UDP behavior in the browser. Sequentially numbered packets let us detect exactly which ones were lost.
What UDP Tests Measure
Packet Loss %
The percentage of packets that never arrive. Under 0.1% is excellent; above 2.5% causes noticeable problems in calls and gaming.
True Round-Trip Latency
Raw latency without TCP retransmission masking. Measured using server-side timestamps for accuracy.
Jitter
Variation in latency between packets. Low jitter means smooth, consistent delivery. High jitter causes choppy audio and rubber-banding in games.
Network Stability
How consistently the connection performs across the full test duration. A stable network shows low variance in all metrics.
Why Results Differ
The analogy
Think of TCP like a postal service that re-delivers lost mail — your packages always arrive, just sometimes late. UDP is like a live phone call — static and dropouts are immediately noticeable, with no replay mechanism to smooth things over.
It is normal for TCP and UDP results to differ. Neither is wrong — they are measuring different things. The gap between them is actually informative: a large gap usually means your network is quietly compensating for problems that real-time applications can't hide.
Good TCP, high UDP packet loss
Your network is dropping packets but TCP is silently retransmitting them. Web browsing may feel normal, but video calls and gaming will suffer. This is the most common case where users are confused — "my speed test looks fine, but my calls are choppy."
Good TCP latency, high UDP jitter
Connection timing is inconsistent but TCP's ordering and retransmission hides it. Downloads complete fine, but video calls have audio dropouts and games feel inconsistent even without visible lag spikes.
TCP and UDP results both good
Genuinely good network quality. Both protocols are performing well — your connection handles both reliable and real-time traffic without issues.
Choosing the Right Test
When in doubt, run both — they take under a minute together. But if you have a specific problem, use this as a guide:
Run: UDP Test
Choppy video and audio dropouts are caused by packet loss and jitter — problems UDP reveals directly.
Run: UDP Test
Games use UDP. Jitter and packet loss cause lag spikes even when your overall speed looks fine.
Run: TCP Test
Web browsing uses TCP. Slow DNS resolution or high TCP handshake time will show up clearly.
Run: TCP Test
File transfers use TCP. Connection setup time and overall latency to major providers is what matters here.
Run: Both Tests
Running both gives you the full picture — reliable and real-time performance, side by side.
Run: Both Tests
Both results together provide the strongest evidence. UDP packet loss is hard to argue with.
Neither test is more accurate than the other
They measure different things. TCP shows how efficiently your connection handles reliable, high-volume traffic. UDP shows the raw quality of the physical connection beneath it. A network with high UDP packet loss but decent TCP latency isn't lying on either test — TCP is just successfully compensating for a problem that UDP can't hide.
Ready to test your connection?
Run both tests and see how TCP and UDP compare on your network.
Run Network Test