What Packet Loss Is
When your device sends data over the internet, it breaks that data into small chunks called packets. Each packet travels independently from your device to the destination. Packet loss is when some of those packets never arrive — they get dropped somewhere along the route and never reach the other end.
For non-real-time applications like file downloads and web browsing, this is handled automatically. The protocol detects the missing packet and requests a retransmission. You might notice slower speeds, but the data eventually arrives intact.
For real-time applications — gaming, VoIP, video calls — packet loss is much more damaging. There is no time to wait for retransmissions. A dropped packet in a voice call means a clipped word. A dropped packet in a game means an action that never registered on the server. Even 1–2% loss is enough to make these applications noticeably worse.
How to Test for Packet Loss
The simplest test uses the ping command in your terminal. Send 100 packets to a reliable server and count how many come back:
Windows: Open Command Prompt and run ping -n 100 8.8.8.8
Mac / Linux: Open Terminal and run ping -c 100 8.8.8.8
When it finishes, look at the summary line. It will show packets sent, received, and lost as a percentage. Any loss above 0% warrants investigation. Above 1% in a sustained test indicates a real problem.
A speed test at speedtesthq.com will also report packet loss if it detects any during the test. This is a quick starting point, though the terminal ping test gives you more control over duration and sample size.
What Causes Packet Loss
Weak Wi-Fi signal: When signal strength is low, data has to be retransmitted at the radio level. If retransmissions fail repeatedly, the packet is dropped. Moving closer to your router or switching to Ethernet eliminates this entirely.
Wi-Fi interference: Heavy traffic on the same channel causes collisions. Multiple retransmissions fail and packets are dropped. Switching to a less congested channel or to 5 GHz often resolves this.
Faulty Ethernet cables: A damaged cable causes electrical errors in transmission. Your network adapter sees the errors and drops the corrupted packet. Replace any cable that is kinked, very old, or has damaged connectors.
Overloaded network equipment: A router or switch that is overwhelmed — too many connections, too high a throughput — drops packets when its buffers overflow. This can happen with older hardware on busy home networks.
ISP congestion: When infrastructure between your home and the internet is congested, routers along the route drop packets rather than let queues grow infinitely. This is the cause when loss persists on a wired connection with good local hardware.
Fixing Packet Loss Based on Where It Occurs
If loss stops on Ethernet but exists on Wi-Fi: The problem is wireless. Solutions include moving closer to your router, switching to 5 GHz, changing your Wi-Fi channel to a less congested one, or upgrading your router if it is old.
If loss exists on Ethernet but disappears when plugged directly into the modem: The problem is your router. Try rebooting it first; if loss continues, your router may need a firmware update or replacement.
If loss exists when plugged directly into the modem: The problem is between your modem and your ISP. This requires contacting your provider with evidence.
If loss only happens when the network is busy: Enable QoS on your router to prevent buffer overflow, and check whether any device is running a very high-bandwidth background task.
Packet Loss Levels and Their Impact
| Loss Level | Impact on Gaming | Impact on VoIP/Video Calls | Impact on Downloads |
|---|---|---|---|
| 0% | No impact | No impact | No impact |
| 1–2% | Noticeable — hit reg issues, brief freezes | Occasional cut-outs and clipped words | Slightly slower, invisible to user |
| 3–5% | Significant — frequent lag, actions lost | Choppy audio, degraded video quality | Noticeably slower retransmissions |
| Above 5% | Unplayable for competitive games | Call quality unusable | Downloads may time out or fail |
How to Prove Packet Loss to Your ISP
If your packet loss test shows consistent loss on a wired connection directly through your modem, you have a legitimate complaint for your ISP. Here is how to document it effectively:
- Connect your laptop directly to the modem via Ethernet (no router in between).
- Run a 100-packet ping test to 8.8.8.8 and screenshot the results, including the loss percentage and timestamp.
- Repeat at different times of day over two or three days.
- Note whether loss is worse at specific times — that pattern suggests congestion rather than a line fault.
- Contact your ISP and tell them specifically: "I have X% packet loss when connected directly to the modem, at times Y and Z, as documented by a ping test to 8.8.8.8." A specific, documented complaint gets resolved much faster than a vague complaint.
Frequently Asked Questions
What is packet loss and why does it matter?
Packet loss is when data packets fail to arrive at the destination. Even 1–2% loss causes voice calls to cut out and game actions to fail to register. Missing data cannot be buffered away — it is retransmitted or lost entirely.
How do I test for packet loss at home?
Open a terminal and run ping -n 100 8.8.8.8 on Windows or ping -c 100 8.8.8.8 on Mac/Linux. The summary will show the percentage of packets lost. A speed test also reports packet loss if detected.
Why does packet loss keep coming back after I restart my router?
A restart fixes temporary issues but not the underlying cause. If loss returns quickly, the problem is persistent — a bad cable, ongoing Wi-Fi interference, a failing modem, or congestion at your ISP.
Is 1% packet loss bad?
Yes, for real-time applications. 1% loss on a VoIP call means dropped words. In gaming it causes hit registration issues and brief freezes. For file downloads, it just slows things slightly since TCP retransmits lost packets automatically.
How do I prove packet loss to my ISP?
Connect directly to the modem with Ethernet, run a 100-packet ping test to 8.8.8.8, and screenshot the results with the timestamp. Repeat at multiple times of day, then contact your ISP with that specific data.
Can Wi-Fi cause packet loss?
Yes. A weak signal, interference, or a congested channel can all cause packets to be dropped. Switch to Ethernet to rule Wi-Fi out — if loss disappears on wired, the problem was wireless.