How the test works
Phase 1 — idle. 40 small requests are sent while the line is quiet. Any request that fails or exceeds 2.5 s counts as lost, and we track the longest consecutive streak (one drop among healthy neighbours is noise; five in a row is a real outage event).
Phase 2 — under load. Six parallel downloads saturate the link for about 12 seconds while we keep probing. Loss that only appears under load is the signature of overflowing router queues — bufferbloat — not a broken line.
Reading your result
| Pattern | Meaning | Fix |
|---|---|---|
| 0% idle · 0% loaded | Healthy | Nothing to do |
| Loss present while idle | Physical layer: WiFi interference, bad cable, failing modem | Test on ethernet; swap the cable; then call the ISP |
| 0% idle · loss (or >150 ms RTT) under load | Bufferbloat — router queue overflows when saturated | Enable SQM/CAKE — usually fixes it completely |
| Heavy loss under load + high RTT everywhere | Oversubscribed ISP uplink | Collect evidence (this page, two runs) and escalate |
Common causes of packet loss at home
- WiFi — the number one cause: interference, distance, or a crowded channel. Ethernet A/B test tells you in one minute.
- Router queue overflow — fixable in software: SQM/CAKE on OpenWrt or any SQM-capable router from our router guide.
- Failing hardware — aged ethernet cables, a dying WAN port, an overheating modem.
- ISP side — overloaded neighbourhood uplink, typically evening-only. Evidence from two runs at different hours supports your ticket.
Related checks
Loss rarely travels alone. Pair this with the bufferbloat test (added latency under load) and a plain ping test (baseline RTT and jitter). All three are free and run in this tab.
FAQ
What is packet loss?
Packet loss is the percentage of data packets that never arrive. On IP networks a little loss (under 0.5%) is normal and corrected silently; above 1-2% you feel it as rubber-banding in games, frozen video calls, and stalling downloads. Loss has causes at every layer: weak WiFi, a failing cable, an overloaded ISP uplink, or a router queue that overflows under load.
How much packet loss is acceptable?
Idle, a healthy line shows 0% (anything under 0.5% is fine). Under full load, a well-provisioned line stays under 1%. Sustained loss above 2% under load means either your ISP uplink is oversubscribed or your router queues are overflowing — the latter is bufferbloat and is fixable with SQM/CAKE; the former needs evidence and an ISP ticket.
Does this test use ICMP like command-line ping?
No. Browsers cannot send raw ICMP packets, so the test times HTTP requests instead — a request that fails or times out counts as lost. This tracks real-world application experience closely (apps also speak HTTP), and typically shows within a fraction of a percent of ICMP-based tools. Run it on ethernet and again on WiFi to isolate wireless problems.