Scroll Wheel Tester
A scroll wheel tester checks whether your mouse scroll wheel correctly sends direction, speed, and delta signals to your computer. Standard notched scroll wheels send 3–5 scroll events per tick; free-spinning wheels (like the Logitech MX Master) can reach 40+ events per second. This free tool uses the browser's WheelEvent API to detect scroll direction (up, down, left, right), measure scroll speed in events per second, report the raw delta value per tick, and identify whether your device uses smooth scrolling (fractional deltas — typical of trackpads and premium mice) or stepped scrolling (integer deltas — typical of standard notched scroll wheels). A scroll wheel that skips, stutters, or scrolls in the wrong direction is one of the most common mouse hardware failures.
Scroll here to detect your wheel
—
Live Speed
—
Personal Best
0
Total Events
Scroll inside the zone above to test passively, or hit Start Speed Test for a 5-second timed challenge. Smooth scroll devices (trackpads) will show fractional delta values.
What Is a Good Scroll Speed?
Scroll speed is measured in events per second (eps) — how many wheel events your mouse sends per second. Here's how different speeds compare.
| Speed | Rating |
|---|---|
| 0–7 eps | Slow |
| 8–14 eps | Normal |
| 15–24 eps | Fast |
| 25–39 eps | Very Fast |
| 40+ eps | Elite |
Smooth Scroll vs. Stepped Scroll: What's the Difference?
Standard mechanical scroll wheels click in discrete notches — each notch fires one event with an integer delta (typically deltaY = 100 or 120 in pixel mode). This is called stepped scrolling. Smooth-scrolling devices like Apple trackpads, the Logitech MX Master in free-spin mode, and most laptop touchpads instead fire many rapid events with small fractional delta values (e.g., deltaY = 4.5, 3.2, 6.0), producing fluid momentum- style movement. This tester detects smooth scrolling by checking whether the deltaY values are fractional. Neither is better for productivity, but smooth scrolling tends to feel more natural on large displays, while stepped scrolling gives more precise control in code editors and spreadsheets.
Frequently Asked Questions
How do I know if my scroll wheel is working properly?
Scroll inside the test zone on this page. If the direction indicator (⬆️/⬇️) updates and the event counter increments, your scroll wheel is sending correct signals to the browser. A healthy scroll wheel should register one event per notch click. If nothing happens when you scroll, try a different browser or check your mouse driver settings.
What is smooth scrolling and how is it detected?
Smooth scrolling produces fractional delta values (e.g., deltaY = 4.666) rather than fixed integer steps (e.g., deltaY = 120). Trackpads (Apple Magic Trackpad, laptop touchpads) and premium mice with free-spinning wheels (Logitech MX Master) typically produce fractional deltas. Standard notched scroll wheels produce integer deltas. This tester shows '✨ Smooth scroll' when fractional deltas are detected.
What does the delta value mean?
The delta value (deltaY or deltaX) is the distance unit reported by the browser per scroll event. A standard mechanical scroll wheel typically sends deltaY = 100 or 120 per notch in most browsers. Smooth-scrolling devices send smaller fractional values per event. The deltaMode property (0 = pixels, 1 = lines, 2 = pages) affects interpretation, but most browsers normalise to pixel mode.
My scroll wheel works in some apps but not others — why?
Scroll behavior is controlled at multiple levels: hardware driver, OS, and application. Some applications intercept scroll events before the browser sees them, or use custom scroll handlers that ignore OS-level smooth scrolling settings. If your scroll works here but not in a specific app, the issue is application-level, not hardware. If it fails everywhere, check your mouse driver (Logitech Options, Razer Synapse, etc.) for scroll direction or speed overrides.
What is events per second (eps) in the speed test?
Events per second (eps) measures how many scroll wheel events your mouse sends in one second. A standard scroll wheel typically fires 3–8 events per second at moderate speed. Enthusiastic scrolling can reach 15–25 eps. High-end mice with free-spinning momentum wheels or fast trackpad flicks can exceed 40 eps. The 5-second timed test measures your average eps across the full duration.
Why does my scroll wheel skip or jump?
Scroll jumping — where the page moves too far per notch — is usually caused by OS scroll speed settings, not hardware. On Windows: Settings → Bluetooth & devices → Mouse → Scroll → adjust 'Lines to scroll at a time'. On Mac: System Settings → Mouse → Scrolling Speed. If the hardware scroll wheel encoder is failing, you may see erratic deltaY values (e.g., mixing +120 and -120 in the same direction), which this tester will show in the delta readout.
Last updated: