Packet loss is the most destructive network problem you can have, and it is invisible on a standard speed test. You can have 500 Mbps download speed and 5% packet loss and your video calls will be completely unwatchable, your game will rubber-band constantly, and your voice will sound like it is being transmitted through a broken radio. Speed tests measure volume. Packet loss is about what does not arrive at all.
The quick answer
Packet loss means some of the data packets your device sends or receives are being dropped and never arrive. Even 1% packet loss causes noticeable problems in real-time applications. The most common causes are a faulty Ethernet or coax cable, a failing network interface card, Wi-Fi interference, or a problem on your ISP's network between your home and their upstream router.
How to test for packet loss
Open a command prompt or terminal and run a continuous ping to a reliable server:
| OS | Command | What to look for |
|---|---|---|
| Windows | ping -n 100 8.8.8.8 | Any "Request timed out" lines = packet loss |
| Mac / Linux | ping -c 100 8.8.8.8 | Final line shows "X packets, Y% packet loss" |
What different levels of packet loss mean
| Packet Loss | Rating | Real-world impact |
|---|---|---|
| 0% | Perfect | No issues |
| 0.1-0.5% | Acceptable | Imperceptible in most applications |
| 1-2% | Noticeable | Gaming lag spikes, occasional call glitches |
| 3-5% | Problematic | Calls break up, games become unplayable |
| 5%+ | Critical | Connection effectively unusable for real-time apps |
How to find where the packet loss is happening
Use traceroute to identify which hop is dropping packets:
- Windows:
tracert 8.8.8.8 - Mac/Linux:
traceroute 8.8.8.8
Look for an asterisk (*) or timeout at a specific hop. If the loss appears at hop 1 or 2, the problem is in your home - your cable, your router, or your network card. If it appears at hop 3 or later, the problem is on your ISP's network and you need to escalate with packet loss documentation.
How to fix packet loss
Physical cable issues (most common)
Replace the coax cable from your wall to your modem. This three-dollar cable fix resolves packet loss for an embarrassingly high percentage of people who call ISP support. Also check Ethernet cables - a bent pin in the RJ45 connector can cause intermittent packet loss that is maddeningly hard to reproduce.
Wi-Fi interference
Wi-Fi packet loss is caused by channel congestion from neighboring networks. Use a Wi-Fi analyzer app to find the least-congested channel in your area and switch your router to use it. Switching from 2.4 GHz to 5 GHz often resolves this immediately - but only if you are close enough to the router. A longer-term fix is running Ethernet, which eliminates the wireless variable entirely.
ISP-side packet loss
Document your traceroute results showing which hop is dropping packets. Call your ISP and specifically say you have "upstream packet loss at hop X, confirmed by traceroute." This gets you escalated to a network engineer rather than first-line support. If the issue is confirmed at their infrastructure, they are obligated to fix it and may offer a service credit for the outage period.
Persistent packet loss combined with high jitter is a strong indicator of a deteriorating physical line or a failing modem. If basic fixes do not resolve it, request a free modem swap from your ISP before buying new hardware yourself.