Mouse Wheel Direction Test
Test if your scroll wheel consistently registers up and down in the correct direction. This tool detects the most common scroll hardware failure: brief direction reversals caused by encoder contact phasing errors — where scrolling down briefly reads as up.
- Scroll up inside the test box — the indicator should show UP consistently.
- Scroll down — the indicator should show DOWN consistently.
- Look for any reversed direction flashes — these are encoder faults.
- Check the direction consistency percentage at the bottom.
Direction reversals almost always occur at the top or bottom of a scroll movement — at the moment you change direction. If reversals only happen at direction changes, the encoder phase relationship is inverted on one contact. If they happen mid-scroll, the encoder is losing electrical contact.
What This Test Measures: Encoder Phase Output
Your scroll wheel encoder uses two contact signals (called A and B channels) in a quadrature encoding scheme. The direction of scroll is determined by which signal changes state first — A before B means "up," B before A means "down." This test reads your browser's wheel event's deltaY value for each scroll step and checks whether the sign (positive or negative) is consistent with your physical scroll direction. If encoder phasing errors are suspected, check whether click-chatter is also present by running a full suite of mouse tests.
A direction reversal in this test means your encoder momentarily sent the wrong phase relationship to your OS — reporting "up" when you scrolled down. This is a hardware electrical signal issue, not a software setting. Every result shown here reflects what your encoder actually sent to your computer, measured in real time from the hardware events arriving at this page.
How to Read Your Direction Test Result
- 100% direction consistency: Encoder is functioning correctly. No direction inversion or phasing error detected.
- Occasional reversal (95–99% consistent): Early-stage encoder wear or dust on the phasing contacts. Consistent with encoder cleaning fixing the issue.
- Frequent reversal (below 95% consistent): Significant encoder degradation. Direction errors will be noticeable in daily scrolling and navigation.
- Systematically inverted (0% or near-0%): Not hardware failure — this is a software or OS "Natural Scroll" setting. Check your OS scroll direction settings (macOS: System Settings → Mouse → Natural Scrolling; Windows: Mouse Properties → Wheel).
What Causes Scroll Direction Errors
- Encoder contact phase imbalance: If one of the two encoder contact strips is more worn or dirty than the other, the phase relationship becomes inconsistent — sometimes A fires before B, sometimes B before A, causing direction errors.
- OS "Natural Scroll" setting: macOS defaults to inverted scroll direction ("Natural Scrolling"). Windows Precision Touchpad drivers and some third-party driver software can invert scroll. This is a software setting, not hardware failure.
- Third-party scroll software: Applications like Logitech Options, MX Master scrolling modes, or SteelSeries GG can remap scroll direction for specific applications. Check if direction errors only happen in certain windows.
- Encoder hardware damage: Physical impact to the scroll wheel assembly can misalign the encoder wheel relative to the contact strips, causing permanent phase reversal. This requires encoder replacement.
How to Fix Scroll Direction Issues
- Software inversion (consistent in all apps): Check OS scroll direction settings. On Windows: Control Panel -> Mouse -> Wheel. On macOS: System Settings -> Mouse -> Natural Scrolling.
- Application-specific reversal: Check your mouse software for per-app scroll direction remapping. Disable application profiles temporarily to isolate.
- Hardware encoder phase issue: Clean the encoder with compressed air and IPA contact cleaner. If direction errors persist after cleaning, the encoder requires replacement — use an EC11 or Alps STEC12E type for most mice.
Scrolling the wrong direction after a system update or mouse driver change? Learn how to diagnose and correct reversed scroll direction in our inverted scroll direction fix guide for Windows and macOS — and check how chattering scroll encoders cause jumpy and inverted scrolling over time.
Most commonly this is a software setting — macOS "Natural Scrolling" or a Windows scroll direction inversion. Check OS mouse settings first. If scroll is only inverted in specific applications, check your mouse software for per-app profiles.
Occasional reversals (1-2 per 50 scrolls) indicate encoder wear or dust — often fixable with compressed air. Frequent reversals indicate significant encoder degradation. Systematic reversal (every scroll event) is almost always a software direction setting, not hardware failure.
Yes, for software inversion. No, for hardware encoder phase errors — software cannot reverse a physically misfiring encoder. The encoder itself must be cleaned or replaced.