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Trackpad Scroll Smoothness Test

This trackpad scroll smoothness test plots every scroll delta. Place two fingers on the trackpad and scroll slowly, then quickly, inside the box. A smooth pad draws a gentle curve, a jerky one spikes.

Two-finger scroll area

Slow, then fast, then with inertia

Live

0 events/s

Delta per event

Scroll with two fingers inside the box.

Smoothness

Events
0
Variation
--
Largest jump
--
Live mouse

Test scroll smoothness

  1. 1. Scroll slowly first

    Even deltas at low speed are the baseline.

  2. 2. Then scroll fast

    Deltas grow but should still change gradually.

  3. 3. Let inertia run

    A smooth tail after lifting fingers is what a good driver produces.

What the numbers mean

Events per second

Modern trackpads deliver 60 to 120 scroll events per second.

Variation

Standard deviation relative to the mean; under 60 percent is smooth.

Largest jump

The biggest change between consecutive deltas, the thing you feel as a stutter.

Live chart

See spikes as they happen and relate them to finger movement.

Smoothness terms

Scroll delta
The amount one wheel event asks the page to move.
Precision touchpad
Windows touchpads with Microsoft drivers that send smooth, high-rate events.
Coefficient of variation
Spread divided by average, used here as the variation percentage.
Inertia tail
Events after the fingers lift, generated by the driver.

Trackpad scroll questions

My Windows laptop scrolls in big jumps. Why?

Non-precision touchpad drivers emulate a wheel with fixed notches. Install Precision Touchpad drivers if available.

MacBook shows huge variation during inertia. Normal?

Yes. The decay from large to tiny deltas raises the variation; judge the slow-scroll phase.

Does this work with a mouse?

Yes, but a notched wheel will always look jerky here. Use the scroll test for mice.

Smooth out trackpad scrolling

Big jumps on Windows

Update the touchpad driver and enable Precision Touchpad.

Events per second under 30

Battery saver or an old driver. Plug in and update.

Random spikes

Dirty or damp pad surface. Wipe it and retest.