This mouse scroll test reads every step your scroll wheel sends and checks it for the faults that make scrolling go wrong. It counts notches up and down, works out what one notch sends to the browser, measures how fast you turn the wheel, and draws each step on a timeline so a worn wheel that jumps the wrong way stands out in orange. It tells notched, high resolution and free spinning wheels apart, and counts wheel tilt and sideways scrolling. It works with any mouse on Windows, Mac, ChromeOS and Linux, and with touchpad scrolling too. The page itself does not move while the pointer is over the scroll box.
How to test your scroll wheel
- Point at the scroll box. The page stops scrolling while the pointer is over it.
- Turn the wheel slowly away from you for 20 notches, one notch at a time. Notches up should rise by 20.
- Turn it towards you for 20 notches. Notches down should rise by 20.
- Spin it quickly in each direction for a couple of seconds. This is when worn wheels jump.
- If your wheel tilts or you have a thumb wheel, push it left and right and watch Sideways.
- Press Speed run 10 s to see how many notches you can turn in ten seconds.
- Press Copy results to keep a record for a warranty claim.
What the results mean
| Readout | What it tells you | Normal result |
|---|---|---|
| Notches up and down | Notches counted in each direction | The number you turned |
| Each step | The size of one step as your browser reports it | Chrome and Edge on Windows send 100 pixels per notch at the default 3 lines, Firefox on Windows sends 3 lines |
| Speed | Notches in the last second, and the highest so far | Higher on a free spin wheel than a notched one |
| Backward jumps | Steps the wrong way in the middle of a scroll | 0 |
| Wheel type | Notched, high resolution or smooth | Matches the wheel you have |
| Sideways | Tilt, thumb wheel and Shift scrolling | Only when you use them |
The verdict under the timeline turns green once you have turned the wheel at least 20 notches each way without a jump.
The page jumps back while you scroll
An orange step on the timeline is a backward jump: you turned the wheel one way and the mouse reported a notch the other way. On a page it looks like a stutter or a short jump back up. The cause is almost always the encoder, the small part that reads which way the wheel turns.
- Dust, hair or fluff in the encoder. Hold the mouse upside down and blow short bursts of compressed air into the gap on each side of the wheel while turning it. Test again.
- Dirty contacts inside. On mice with a mechanical encoder, a drop of contact cleaner on the encoder, with the mouse opened, clears the problem for a while. Only do this out of warranty.
- A worn encoder. If jumps come back soon after cleaning, the encoder is worn. A repair shop can replace it, but on a cheap mouse a new mouse costs less.
- Not the wheel at all. If jumps happen only in one app, check that app's scroll settings before blaming the mouse.
The wheel misses notches
If you turn 20 notches and the count rises by fewer, steps are not reaching the computer. Dirt in the encoder causes this too, so clean it first. On a wireless mouse, a weak battery or a receiver far from the mouse drops wheel steps along with movement: plug the receiver into a port on the computer itself and fit a fresh battery. If movement also stutters, the guide for mouse lagging covers the other causes.
One notch scrolls too far or not far enough
When the counts are right but pages move the wrong amount, the cause is a setting, not the wheel:
- Windows 11: open Settings, then Bluetooth and devices, then Mouse. Change Lines to scroll at a time, or set Roll the mouse wheel to scroll back to Multiple lines at a time.
- Windows 10: open Settings, then Devices, then Mouse, and use Choose how many lines to scroll each time.
- Mouse software: Logi Options+, G HUB, Razer Synapse and similar apps can add their own scroll speed, acceleration or smooth scrolling. Turn those off to compare.
- Browser zoom: pages zoomed in move fewer pixels per notch. Press Ctrl + 0 to reset zoom.
Scrolling goes the wrong way every time
If every step lands on the wrong side of the line, a setting has reversed the wheel. On a Mac, turn off Natural scrolling in System Settings, then Mouse. On Windows 11, open Settings, then Bluetooth and devices, then Mouse, and set Scrolling direction to Down motion scrolls down. Windows 10 has no such switch, so check the mouse maker's app there. A touchpad has its own setting under Settings, then Bluetooth and devices, then Touchpad, then Scroll and zoom.
Tilt, thumb wheels and high resolution wheels
Many mice send sideways scrolling when you tilt the wheel or turn a thumb wheel. The test counts these under Sideways, separately from Shift and wheel, which Windows also turns into sideways scrolling. A tilt held down repeats, so one push can add several steps.
High resolution wheels split each notch into several smaller steps, so pages glide. Free spinning wheels, such as the ones on many Logitech mice, also send lots of steps quickly. Both are normal. If the free spin wheel slips when you press it, run the middle click test to count those slips.
What a mouse scroll test cannot see
The browser only receives what the mouse and the system send. It cannot count physical notches, feel how stiff the wheel is or hear a squeak. On a Mac, the system speeds up fast turns, so step sizes vary and fast notch counts are estimates. To check the buttons and the rest of the mouse, use the mouse tester, and the polling rate test to see how often it reports movement. If the mouse stops responding altogether, start with the guide for a mouse not working.
Scroll wheel questions
How do I know if my scroll wheel is broken?
Turn it slowly 20 notches one way, then 20 the other, over the scroll box. A working wheel adds one step per notch in the right direction and shows no backward jumps. Jumps in orange, notches that add nothing, or steps in both directions from one turn all point to a dirty or worn encoder.
Why does my mouse scroll up when I scroll down?
If it happens now and then during a scroll, the wheel's encoder is misreading its position, usually because of dust or wear. This test counts those backward jumps. If it happens every time, it is a setting: natural scrolling on a Mac, Scrolling direction in the Windows 11 mouse settings, or reversed scrolling in the mouse software.
Why does one notch scroll more than three lines?
Windows scrolls 3 lines per notch by default, and the number is set in Settings, then Bluetooth and devices, then Mouse, under Lines to scroll at a time. Mouse software can add its own speed or acceleration on top, and macOS speeds up fast turns.
What is a high resolution scroll wheel?
It sends several small steps for each notch instead of one big one, so pages move more smoothly. This test reports it as High resolution with the number of steps per notch. Apps that ignore the small steps may feel slower to scroll with it.
Can I test touchpad scrolling here?
Yes. Two finger scrolling on a touchpad sends the same wheel events as a mouse, so the counters and the timeline work. It shows as a smooth wheel with steps of different sizes. For the touchpad surface itself, use the touchpad test.