M-Lab NDT review
A focused, open-source tool for TCP upload and download measurement.
Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026
M-Lab NDT is an open-source network measurement tool for testing Internet connection performance. It measures application-level upload and download performance between a client and an M-Lab server through single-stream TCP tests. Web, Android, and API access make it suitable for public speed-test services, developers, researchers, regulators, operators, and teams that need reusable network measurement data rather than a conventional commercial SaaS product.
Its developer and data ecosystem is the main differentiator. The browser-based JavaScript client, reference Go client, and command-line tool support different integration paths, while JSON test output fits automated workflows. Server discovery is handled through the Locate API. NDT7 uses WebSocket and TLS over TCP, and the published protocol support also includes NDT5 and web100. Public raw, visualized, and queryable test data extend the tool beyond individual measurements, with BigQuery datasets and views available for analyzing NDT results.
The scope is deliberately focused: NDT performs active, single-stream TCP upload and download testing rather than presenting a broad network-testing suite. That makes it a strong choice for teams building public Internet performance measurements, analyzing open datasets, or integrating speed tests into web and developer applications. The reference server implementation also supports self-hosting. Teams seeking wider test methods or a conventional paid service with tiered commercial controls should consider a different category fit; teams prioritizing open measurement infrastructure and accessible results should pick M-Lab NDT.
M-Lab NDT pros and cons
- Where it wins
- Free open-source single-stream TCP upload and download testing
- JSON output, server discovery, and browser and Go clients
- Public datasets with BigQuery views for NDT results
- Where it doesn't
- Measures single-stream TCP performance rather than broad network conditions
- Focused on upload and download testing instead of wider test coverage
- Self-hosting requires using the reference server implementation
M-Lab NDT fact sheet, pricing and score →
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