Scroll Wheel Test

How to use

1. Choose Steady-direction diagnostic and select Up / negative ΔY only, Down / positive ΔY only, or Mixed / explore.
2. Press Start, keep the surface focused, and scroll steadily inside it. For a one-direction run, avoid intentionally reversing direction.
3. Stop and inspect vertical and horizontal browser events, deltaMode units, opposite-direction events, relative magnitude outliers, and the recent event trace.
4. For a timed comparison, choose Timed wheel-event rate with a 5s, 10s, or 30s window, then compare only the same device, input style, browser, OS settings, and setup.
5. Repeat unusual browser evidence before interpreting it. This page reports WheelEvent records, not a physical wheel or encoder diagnosis.

What the result means

• Browser wheel events are WheelEvent records, not physical wheel notches. deltaMode 0, 1, and 2 define pixels, lines, and pages for deltaX/deltaY.
• Negative ΔY is treated as the Up side and positive ΔY as the Down side for this browser diagnostic. Natural Scrolling, trackpads, and OS settings can make physical gesture intuition differ.
• Opposite-direction events are vertical browser events whose sign conflicts with the direction declared for a controlled run. They are evidence to repeat, not proof of encoder damage.
• Relative delta spikes are vertical magnitudes greater than 4× this run's median absolute delta magnitude when all relevant samples share one deltaMode. Mixed pixels, lines, and pages are not combined.
• Timed event rate is browser WheelEvent records divided by the run's actual elapsed seconds. It is browser cadence, not physical speed, RPM, or notches per second.
• Horizontal events may come from a tilt wheel, side wheel, trackpad, or gesture input; a WheelEvent does not identify exact hardware or guarantee that page content scrolled.

Limitations

• WheelEvent can come from a mouse wheel, trackpad, or similar input; the browser does not identify exact wheel hardware.
• deltaX and deltaY units depend on deltaMode and cannot be assumed to be pixels. Pixel-, line-, and page-based deltas are not combined into one magnitude diagnostic.
• Natural Scrolling, OS settings, touchpad inertia, smooth scrolling, browser behavior, and user gesture can affect direction and magnitude.
• A wheel event does not necessarily imply that page content actually scrolled; it can occur on an unscrollable surface or participate in other browser behavior.
• Browser events cannot reveal physical detents, encoder electrical pulses, missed physical notches, or RPM. A repeated browser anomaly can motivate comparison on another browser or device, but one run does not prove hardware damage.

Troubleshooting

The direction looks reversed

Check whether you selected the correct expected browser direction. Natural Scrolling, trackpad behavior, and OS settings can change the sign you expect. Repeat a controlled one-direction run.

I see one opposite-direction event

Repeat the same steady one-direction protocol. A single event can come from gesture variation, inertia, OS/browser behavior, or the device; it is not a hardware verdict.

Delta values vary a lot

First check Delta unit(s). Do not compare pixel, line, and page values directly. Smooth-scroll devices and trackpads can naturally produce variable magnitudes.

I see Mixed delta units

This run contains incompatible WheelEvent units, so DeviceMetrik does not combine the magnitudes. Repeat under one consistent device, browser, and input setup.

Event rate changes between runs

Compare only the same duration, device, input style, browser, OS settings, and similar background conditions. Browser events/sec is not physical wheel RPM.

Related tools

• Mouse Test

  Test mouse buttons, side buttons, held states, wheel events, and pointer movement online. See live browser event counts, hold times, movement path, and session status.

• Mouse Double Click Test

  Test a mouse for unintended double clicks with slow single-click screening or intentional pair timing. Choose a button, inspect browser click intervals, and compare local runs.

• Mouse DPI Test

  Estimate mouse DPI/CPI from browser Pointer Lock movement over a measured horizontal distance. Run three trials and review median, range, drift, input mode, and local history.

• Mouse Polling Rate Test

  Run a mouse polling rate test from browser-observed pointer movement. Review median Hz, intervals, timing variation, coalescing context, Pointer Lock, and local history—not raw USB telemetry.

FAQ