Measures round-trip time (RTT) to several Cloudflare edge locations at once, so you can judge your network quality to different regions and diagnose why overseas sites feel slow.
Lower is better: under 50ms feels smooth, around 100ms is acceptable, above 200ms feels laggy. Results depend on physical distance and carrier peering — run it a few times and look for a stable value.
Avoid large downloads while testing, and keep the tab in the foreground: background tabs get their timers throttled by the browser.