LibreSpeed

LibreSpeed is a browser-based speed test you host yourself, measuring download and upload throughput plus latency and jitter from any modern browser without Flash or plugins. It comes in PHP, Go, Rust and Node backends, can split the frontend and the measurement servers across machines, and optionally stores results, shares them and reports the client address and ISP.

People run it on their own server to measure the link users actually get, rather than trusting whichever commercial test node happens to be nearest.

Self-hosting means the line is measured without a third party choosing the server, there is no account or per-test fee, and the whole thing is one binary and a folder to back up.