NDT7
Network Diagnostic Tool version 7. The open-source protocol used by M-Lab to measure internet speed without ISP bias.
What NDT7 means
NDT7 stands for Network Diagnostic Tool version 7. It is an open-source protocol developed and maintained by Measurement Lab (M-Lab), a non-profit research organization focused on internet measurement. DSLspeedtest.biz uses NDT7 to run speed tests because it is transparent, reproducible, and designed to measure your connection to the actual internet rather than to a nearby server on your ISP's own network.
The NDT7 protocol measures your download speed, upload speed, and latency by establishing a connection to an M-Lab server and transferring data using standard TCP/IP, the same protocol your browser uses for everyday web traffic. This means the test reflects realistic conditions rather than optimized conditions.
One key feature of NDT7 is that all data collected during a test is published publicly. Researchers, journalists, and regulators use M-Lab data to study internet access quality around the world. Your test result contributes to this dataset unless you opt out.
Why NDT7 matters for your connection
Some speed test providers use servers located on your ISP's own network. This can give inflated results that do not reflect your connection to outside services like Netflix, Google, or any other website you actually use. M-Lab servers are hosted at internet exchange points that are independent of ISPs, making the results a better measure of your real-world connection to the broader internet.
Using an open-source protocol also means the measurement method is fully documented and auditable. There is no proprietary algorithm that could be adjusted to favor certain results. Learn more in our guide on how our speed test works.
NDT7 at a glance
| Feature | NDT7 |
|---|---|
| Protocol | Open source, WebSocket over TCP |
| Server operator | Measurement Lab (M-Lab) |
| Data policy | Results published publicly |
| Metrics measured | Download, upload, latency, jitter |
| Server location | Internet exchange points (ISP-neutral) |
Common questions about NDT7
NDT7 measures your connection to the general internet, not to a server inside your ISP's network. Other tests that use servers on your ISP's infrastructure can show higher speeds that do not represent real-world performance on outside services. NDT7's results are more honest about what you actually experience.
M-Lab publishes speed test results publicly as part of their research mission. The data includes your test results and approximate location, but it is anonymized and not tied to personal identifiers. You can review M-Lab's data policy at measurementlab.net.
NDT7 is the current version of the tool. It uses WebSocket and a modern server architecture that is easier to deploy and maintain. NDT5 used a different protocol (TCP over port 3001) that is now deprecated. NDT7 provides the same core measurements with improved reliability.
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