How to run an accurate speed test

When measuring Internet speed, look beyond the Mbps number. Throughput, latency, jitter and packet loss describe different properties, while Wi-Fi, Ethernet, competing devices, VPNs, routing and the test server all affect results. High throughput can coexist with poor latency under load.

How to find the bottleneck

Separate the LAN from the ISP path: check signal or cable, then ping while idle and under transfer, then throughput. Repeat measurements under controlled conditions. A problem that occurs only in the evening, only through a VPN, or only toward one destination points to different bottlenecks.

The detail that matters

For a reproducible baseline, use Ethernet when possible, stop competing transfers, record whether VPN is enabled, and repeat against suitable servers. Compare several runs rather than selecting the highest number; browser/device CPU, Wi-Fi, server load and path selection can all cap a result. For a control measurement, use 2ip speed test.