What Packet Loss Actually Is

Packet loss happens when a chunk of data leaves your device and simply never arrives — no error message, no retry prompt, just a gap. What happens next depends entirely on the protocol carrying that data. Downloads, web pages, and file transfers run over TCP, which detects the missing packet and automatically retransmits it. You barely notice; the page loads a fraction of a second slower and the file arrives intact. Real-time traffic — games, voice chat, video calls — runs over UDP, which has no built-in retransmission. A lost UDP packet is just gone. The game has to guess what happened in that missing frame, and it usually guesses wrong, which is why 1-2% packet loss can feel unplayable in a shooter while your Netflix stream or file download shows nothing unusual at all.

Why checkping.io Measures Real UDP Loss, Not an ICMP Estimate

Most "packet loss test" tools online are actually running ICMP ping in a loop and reporting how many echo replies came back. That is a reasonable proxy, but ICMP traffic is a different protocol from what games actually send, and many routers and firewalls deprioritize or rate-limit ICMP separately from real application traffic — which can make a connection look worse (or better) than it actually performs in a match. checkping.io takes a different approach: it opens a WebRTC connection through a TURN relay and sends a continuous stream of UDP datagrams, then counts exactly how many fail to arrive at the other end. That is real UDP packet loss, measured with the same transport-layer behavior your game client uses, not an ICMP stand-in. It is more honest about what you will actually feel in-game, because it is subject to the same queuing, radio retransmission, and routing behavior that your actual game traffic goes through.

How to Run a Packet Loss Test Properly

A single 5-second test tells you very little. Packet loss is inherently bursty — a Wi-Fi interference event or a router queue overflow might only last a second or two — so a short sample can easily miss the problem entirely or catch an unrepresentative spike. Run the test correctly:

Run it three or more times. A single run can catch a fluke; a pattern across multiple runs is the real signal.
Test idle, then test under load. Run the packet loss test with nothing else active, then start a large download or a 4K stream on another device and run it again. A jump in loss under load usually means your router's queues are overflowing, not that your ISP line is inherently bad.
Test on Wi-Fi, then on Ethernet. If loss disappears on a wired connection, the source is almost certainly wireless interference, not your ISP.
Test at peak hours and off-peak hours. Run one test during your normal evening play session (roughly 7 PM to 11 PM) and one late at night or early morning. Loss that only appears during peak hours points at neighborhood or ISP congestion rather than anything in your home.

What Each Loss Percentage Means

Packet loss	Rating	What you will notice
0-0.5%	Fine	Effectively invisible. Game netcode absorbs occasional single drops without any visible effect.
0.5-2%	Noticeable	Occasional missed hits, brief voice clipping, small stutters in fast-paced games.
2-5%	Bad	Regular rubber-banding, choppy movement, frequent hit registration failures, voice calls breaking up.
5%+	Unplayable	Frequent disconnects, frozen video calls, competitive play essentially impossible.

These are typical ranges rather than hard limits — a game with generous lag compensation tolerates more loss than a fighting game built around tight rollback netcode. Treat the table as a starting point, not a strict verdict.

Command-Line Alternatives

A browser test is fast and convenient, but the command line gives you longer sample windows and can help localize exactly where loss starts.

Windows — long ping run: ping -n 100 1.1.1.1 sends 100 pings and reports a loss percentage at the end. A count that low (50 pings or fewer) can miss a brief but real burst of loss, so 100 or more is worth the extra thirty seconds.
macOS/Linux — long ping run: ping -c 100 1.1.1.1 does the same thing; the summary line at the end reports packets transmitted, received, and percent loss.
Windows — pathping: pathping 1.1.1.1 traces the full route to the destination and then measures loss at every hop along the way over several minutes. This is the tool for localizing loss: if loss appears at your router (hop 1) it is a home network problem, and if it starts two or three hops later it usually points at your modem, your ISP's local equipment, or the line into your home.
macOS/Linux — mtr: the closest equivalent to pathping, combining traceroute and ping into one continuously updating per-hop loss report.

What Packet Loss Feels Like, App by App

The same underlying loss percentage produces very different symptoms depending on what you are doing:

Gaming: rubber-banding (your character snaps back to an earlier position), delayed ability activations, and shots that clearly landed doing nothing. Movement looks choppy because the client is filling in gaps with guesses instead of real position updates.
Voice chat: robotic or metallic-sounding audio, dropped syllables, and words that cut out mid-sentence. Voice codecs try to conceal small gaps by stretching or repeating adjacent audio, which is what produces that distinctive robotic artifact.
Video calls: frozen frames, blocky pixelation right after a freeze, and audio that drifts out of sync with video as the call tries to catch back up.

Where Packet Loss Usually Comes From

In rough order of likelihood, packet loss originates in one of these places:

Wi-Fi (most common). Interference, weak signal, and channel contention cause radio retransmissions that show up as loss. Quick isolation step: plug in an Ethernet cable and re-test. If the loss disappears, it was wireless.
Cabling or router hardware. A damaged Ethernet cable, a failing port, or a router struggling under load (old firmware, high CPU, too many connected devices) can drop packets even on a wired connection.
Your ISP. Degraded infrastructure, a failing modem, or congestion at a shared node can introduce loss beyond your router. This is where pathping or mtr becomes essential — loss that starts a couple of hops past your router and continues to the destination is evidence you can hand directly to ISP support.
The far end (rare). Occasionally the loss is on the game server's side or the route to it, not your connection at all — worth confirming by checking if the problem happens in every app or only in one specific game.

Once you have isolated roughly where the loss is happening — home network, ISP, or destination — the fix itself usually takes only a few minutes. For the full step-by-step troubleshooting process, including router firmware checks, driver updates, and exactly what to tell ISP support, see our companion guide on how to fix packet loss. And if your loss numbers look fine but gameplay still feels inconsistent, the culprit may not be loss at all — see jitter vs. ping for the other metric that predicts how a connection actually feels in real time.