What Does Packet Loss Mean?

What a "packet" is

All data on the internet travels in discrete chunks called packets. A web page, video stream, voice call, or game update is broken into thousands of small packets, sent across the network, and reassembled at the destination. Each packet contains header information (where it came from, where it's going) and a chunk of payload data — typically 1,500 bytes for standard Ethernet frames.

Packet loss occurs when one or more of these packets fails to arrive. A router along the path may drop it due to overload, a wireless connection may corrupt it, or a cable fault may simply lose it in transit.

Packet loss percentage and its real-world effect

Packet loss	Gaming	Voice / video call	File downloads (TCP)
0%	Perfect	Perfect	Full speed
0.1–0.5%	Occasional rubber-banding	Barely noticeable	Slight speed reduction
1–2%	Noticeable lag spikes	Audible audio glitches	TCP speed reduced 10–30%
3–5%	Significant desync, unplayable	Choppy, broken sentences	TCP speed reduced 50–70%
Above 5%	Unusable	Call breaks down entirely	Downloads stall, timeout

Why 1% packet loss hurts more than it sounds

TCP — the protocol used for most internet traffic — responds to packet loss by assuming network congestion and dramatically reducing its sending rate. When a packet is lost, TCP halves its congestion window and waits for a retransmission acknowledgement before continuing. This can cause a download that would take 10 seconds to instead take 30–60 seconds, depending on the pattern of loss.

Real-time applications (voice calls, gaming, live video) use UDP rather than TCP, so they don't retransmit lost packets — they simply skip them. This causes audible glitches, visual artifacts, and desync rather than slowdowns.

Common causes of packet loss

Network congestion

When a router or network link is overwhelmed with more traffic than it can handle, it drops packets rather than queue them indefinitely. This is the most common cause of packet loss on the internet. ISP congestion during peak hours is a frequent culprit.

Faulty hardware

A damaged Ethernet cable, a failing network adapter, or a defective router port can cause intermittent packet loss. Physical layer problems — bent cables, damaged connectors, or water-damaged hardware — are common causes of persistent low-level packet loss.

Wi-Fi interference

Wi-Fi packets corrupted by interference are discarded rather than forwarded. At the Wi-Fi layer, corrupted frames are retransmitted automatically, but this still registers as loss at the IP layer when the retransmission budget is exceeded. Switching to 5 GHz or using Ethernet eliminates this source entirely.

Distance to server

Long routing paths across many network hops increase the probability that at least one hop along the path is congested or experiencing issues. When testing against a remote server, some packet loss may be happening far outside your ISP's network.

How to test for packet loss

Run the Packet Loss Test on Speedtest.now — it sends 100 probe packets to the nearest test server and reports the percentage that were lost. A healthy connection should show 0% loss. Anything above 1% warrants investigation.

If you see packet loss on the Speedtest.now test, also run: ping -c 100 8.8.8.8 from a terminal to determine whether the loss is between you and the internet generally, or specific to the test server.

How to fix packet loss

• Replace suspect Ethernet cables — Cat 5e or Cat 6 cables with damaged shielding cause intermittent loss
• Switch from Wi-Fi to Ethernet — eliminates radio interference as a source
• Restart your router and modem — clears stale routing tables and buffer states
• Connect to a closer server or endpoint — reduces path length and the number of hops
• Contact your ISP — if loss is consistent on Ethernet at multiple times of day, the problem is likely in their infrastructure