Packet loss test — see the bullets that never arrived

Packet loss, in one sentence: some of the tiny messages your PC sends to the game server never arrive — and in a shooter those messages are your shots, so loss means shots that never registered. Speed tests won’t show it (they quietly resend lost data and average the difference away). The test below starts automatically, probes your line for 25 seconds, and tells you straight: clean, or losing packets — and if you’re losing them, where to look first.

What is packet loss?

Your game talks to its server in packets — tiny messages sent 20 to 60 times a second carrying your position, your inputs, your shots. Packet loss is when some of them never arrive. There’s no resend in game traffic: a lost packet is simply gone, so the server never saw the shot and your screen fills the gap with a guess. That’s the killcam where you’re already behind the wall, the rubber-band back to where you stood two seconds ago, the voice chat that turns robotic.

Why your speed test says you’re fine

Speed tests run over TCP — the protocol that silently retransmits anything that goes missing. From the test’s point of view nothing was ever lost; the transfer just took a hair longer, and that difference disappears inside an average. Games use UDP, which never retransmits. So a speed test can hand you a clean bill of health on a line where your game is losing 3% of everything it sends. If your speed test says fine but you still lag, this is the whole story.

How to fix packet loss, by cause

1. Wi-Fi interference — the most common cause by a mile. Your signal can be full bars and still drop packets to a neighbor’s router, a microwave, a wall. Fix: one Ethernet cable. If that’s impossible, measure your own Wi-Fi link and move to a cleaner channel.
2. A bad Ethernet cable or port — a damaged cable, a loose connector, or a dying router/NIC port drops packets under load. Fix: swap the cable for a known-good one and try another router port; if the loss vanishes, you found it in five minutes.
3. ISP node congestion — if loss shows up every evening and vanishes at 3 AM, it’s the neighborhood node your ISP oversubscribed, not your house. Fix: you can’t rewire their network, but you can make them — run the full monitor during the bad hours and bring timestamped proof they can’t wave away.
4. Bufferbloat — when someone saturates the line, a bloated router queue first delays, then starts discarding packets — your game packets included. Fix: run the full monitor’s 8-second stress test to confirm, then enable SQM/Cake — the bufferbloat guide walks through it.

Frequently asked questions

What is packet loss?

Some of the small messages your computer sends never arrive at the other side. In a game those messages carry your shots and movement — so loss means shots that never registered and movement that snaps back.

What’s a good packet loss %?

0% is clean. Anything above ~1–2% is felt in-game — rubber-banding, shots that don’t register, robotic voice chat. Between 0 and 1% most players won’t notice, but watch it if it comes in bursts.

Why do I have packet loss with fast internet?

Speed and loss are different things. A 500 Mbps line still drops packets to Wi-Fi interference, a failing cable or port, a congested ISP node, or a router queue so bloated it discards traffic — and your speed test retransmits over TCP, so it never tells you.

How do I fix packet loss?

Match the fix to the cause — Ethernet instead of Wi-Fi, a new cable or port, SQM/Cake for bufferbloat, or timestamped evidence for an ISP-side problem. The ranked list above has the one-line fix for each.

Does packet loss cause lag?

Yes — it’s one of the four killers, alongside lagspikes, jitter and bufferbloat. A line can have a perfect average ping and still play terribly at 2% loss.