What this test measures
A speed test measures how fast your connection is for a few seconds at its best. Most connection complaints aren’t about speed, though. They’re about calls that freeze every few minutes, games that lag at random, and video that stalls and then recovers. That’s stability, and you can only see it by measuring for longer.
This test sends 20 small UDP packets a second, the same kind of traffic calls and games use, to Cloudflare’s nearest location and back. It splits the run into 30-second stretches and looks for:
- Drop-outs: 1 second or more where nothing gets through at all. Long enough to freeze a call or disconnect a game.
- Packet loss: packets that never arrive, overall and in each 30-second stretch, so a short burst isn’t averaged away.
- Latency spikes: stretches where delay jumps to 3 times its normal level (and at least 30 ms above it). Usually a sign that something else is filling the connection.
- Jitter: how much the delay changes from one packet to the next. High jitter makes calls stutter even when nothing is lost.
Want a quick check instead? The 20-second packet loss test measures loss, latency and jitter right now and rates your connection for calls, games and streaming.
What counts as a stable connection?
The test gives one of three verdicts. Stable means every stretch looked the same. Mostly stable means there were small problems you might notice on a call. Unstable means at least one problem bad enough to drop a call or a game. These are the limits it uses:
| Measure | Stable | Unstable |
|---|---|---|
| Drop-outs | None | Any gap of 1 s or more with nothing getting through |
| Packet loss, whole test | Under 0.5% | Over 2% |
| Packet loss, worst 30 s | Under 2% | Over 5% |
| Latency spikes | None | In a quarter or more of the test |
| Jitter | Under 30 ms | — |
Anything between the two columns is “mostly stable”.
Is it your Wi-Fi or your line?
The quickest way to find out is to run the test twice. The result page compares each run with your last one, so you can see the two side by side.
- Run it on Wi-Fi, where you normally use your computer.
- Run it again on a cable, plugged straight into the router with Ethernet.
If the cable run is stable and the Wi-Fi run isn’t, the problem is your Wi-Fi: try moving closer to the router, switching to the 5 GHz or 6 GHz band, or adding a mesh node. If both runs are unstable, the problem is more likely your router, your modem or your ISP. Restart the router and modem, and if that doesn’t help, contact your ISP. For loss in particular, see How to fix packet loss.
Why 5 minutes isn’t 5 days
A few minutes of measurement can tell you whether your connection is stable now. It can’t tell you about the drop-out that happens every evening at 8 pm, or the router that restarts itself at 3 am. Those are often the problems people actually call their ISP about, and an ISP will usually ask for evidence that covers more than one test.
Monitor your connection 24/7 with PeakHour
PeakHour sits in your Mac menu bar and measures packet loss and latency around the clock, to every hop between you and the internet. It alerts you when your router or the internet becomes unreachable, and keeps the history, so you can see exactly when problems happened and whether they started on your Wi-Fi, your router or your ISP.
More on what PeakHour monitors: Mac network monitor and router and ISP monitoring.
How the test works
The test uses the same engine as our packet loss test. Your browser opens a WebRTC data channel set to unordered, with no retransmits, relayed over UDP through Cloudflare’s TURN service, and sends numbered packets to itself. Because one browser both sends and receives, both ends share a clock, so every packet’s delay is exact and every missing packet really was lost. A 5-minute run sends 6,000 packets and uses under 3 MB of data.
What it covers: your device, your Wi-Fi, your router and your ISP’s access network, which is where most home connection problems start. It doesn’t test the route to a particular game server or call service, and it combines upload and download into one result.
Frequently asked questions
What is an internet stability test?
A stability test measures your connection continuously for several minutes and looks at how much it changes: whether it drops out, loses packets in bursts, or suddenly gets slower to respond. A speed test tells you how fast your connection is at its best. A stability test tells you whether it stays that way.
How long should an internet stability test run?
At least 5 minutes. A 20-second test can only catch a problem that happens during those 20 seconds. Five or ten minutes is long enough to catch Wi-Fi drop-outs and lag spikes that happen every minute or two. Problems that come back once an evening or once a day need continuous monitoring over several days.
What counts as a stable internet connection?
No drop-outs (a drop-out here is 1 second or more with nothing getting through), packet loss under 0.5% overall with no 30-second stretch above 2%, and no lag spikes, where delay jumps to 3 times its normal level. Jitter, the change in delay from one packet to the next, should stay under about 30 ms.
Why does my internet keep dropping out?
The most common cause is Wi-Fi: a weak signal, interference from neighbouring networks, or a device switching between access points. After that come a busy connection (backups and downloads filling the line), a router that needs a restart or a firmware update, a damaged cable or connector, and faults on your ISP’s side.
How do I tell if the problem is my Wi-Fi or my ISP?
Run the test twice: once on Wi-Fi, then again with your computer plugged into the router with an Ethernet cable. If the cable result is stable and the Wi-Fi result isn’t, the problem is your Wi-Fi. If both are unstable, the problem is more likely your router, your modem or your ISP.
Is a stability test the same as a speed test?
No. A speed test fills your connection for a few seconds to measure its top speed. A stability test sends a light, steady stream of small packets for several minutes and checks whether each one arrives, and how long it takes. A connection can pass a speed test easily and still drop out every few minutes.
Do I need to keep the tab open?
Yes. Keep the tab in front, with the screen on, until the test finishes. Browsers slow down background tabs to save power, which would make a healthy connection look unstable, so the test stops if you switch away.
Do you store my IP address?
No. Your IP address is used for a moment to stop abuse and is never stored. Your last result is kept only in your own browser, so the next run can compare against it.
How do I monitor my internet stability all the time?
On a Mac, PeakHour monitors your connection around the clock from the menu bar. It records packet loss and latency to every hop between you and the internet, alerts you when your router or the internet becomes unreachable, and keeps the history so you can show your ISP exactly when the problems happened.