How Our Speed Test Works
Transparent methodology using the open-source NDT7 protocol.
The NDT7 Protocol
DSLspeedtest.biz uses NDT7, the seventh version of the Network Diagnostic Tool developed and maintained by M-Lab (Measurement Lab). M-Lab is an open, neutral platform for internet research supported by organizations including Google, Mozilla, and the Open Technology Institute.
NDT7 measures your connection by transferring data between your browser and the nearest M-Lab server using WebSocket connections. Because the measurement goes to a neutral third-party server rather than an ISP-operated one, the result reflects your true connection quality, not an optimized path.
What Happens During a Test
Server Selection
The client automatically selects the nearest M-Lab server to minimize the effect of geographic distance on your results.
Latency Measurement
Multiple round-trip time measurements are taken to calculate your ping and jitter before the throughput test begins.
Download Test
Data is transferred from the M-Lab server to your device over a WebSocket connection for approximately 10 seconds. The maximum sustained throughput is recorded as your download speed.
Upload Test
Data is transferred from your device to the M-Lab server. The maximum sustained throughput is your upload speed.
Factors That Affect Results
- WiFi interference or weak signal
- Number of devices sharing your connection
- Network congestion at peak hours (evenings, weekends)
- ISP throttling of certain traffic types
- Age and capability of your router or modem
- Distance from your home to the telephone exchange (for DSL)