What Is the Scroll Test?
A scroll test is a diagnostic tool that measures the behavior of your mouse scroll wheel. It detects scroll direction (up or down), the delta value (how much each scroll step moves), the number of scroll events per second, and the smoothness of your scrolling. This tool is useful for diagnosing scroll wheel issues, testing scroll speed, and verifying that your mouse is functioning correctly. Whether you are a gamer who relies on scroll wheel binds, a designer who scrolls through long documents, or a developer testing scroll-based interactions, this tool gives you real-time feedback on your scroll wheel performance.
How It Works
The test listens for wheel events within the designated area. Each time you scroll, the browser fires a wheel event containing a deltaY value that indicates the direction and magnitude of the scroll. The tool records each event timestamp, calculates the interval between events, and derives your scroll rate in events per second. The smoothness metric is based on the consistency of intervals between events — more consistent intervals indicate smoother scrolling. The total accumulated delta shows how much virtual distance you have scrolled during the session.
How to Use
- Place your cursor inside the test area.
- Scroll your mouse wheel up or down.
- Watch the real-time display for direction, delta, events per second, and smoothness.
- The tool resets automatically when you stop scrolling for a moment.
- Use the Reset button to clear all data and start fresh.
Tips & Information
Test Both Directions
Scroll both up and down to verify your mouse wheel works correctly in both directions. Some mice develop issues in one direction before the other due to asymmetric wear on the encoder.
Check for Skip
If events per second are lower than expected or the delta values are inconsistent, your scroll wheel encoder may be skipping. This is a common issue with older mice and can often be fixed by cleaning the encoder.
Compare Smoothness
Smooth scrolling mice produce consistent intervals between events. If you see erratic intervals, your mouse may not support smooth scrolling or the feature may be disabled in your OS settings.
Test Different Speeds
Try scrolling slowly and rapidly to see how your mouse handles both. Some mice have different delta values at different scroll speeds, which can affect how applications interpret your scrolling.
Frequently Asked Questions
What is scroll delta?
Scroll delta is the value the mouse sends with each wheel event, representing how far the scroll should move. Standard mice typically send delta values of 100 to 120 per notch, while smooth-scrolling mice send smaller, more frequent deltas.
Why is my smoothness score low?
Low smoothness means the intervals between your scroll events are inconsistent. This can be caused by a notch-based scroll wheel (which is naturally less smooth), dirt in the encoder, or system-level scroll settings.
Can this test detect hardware problems?
Yes. If events are not registered, the delta is zero, or events fire without scrolling, these indicate potential hardware issues with your scroll wheel encoder or the mouse firmware.
Does this work on laptops with trackpads?
Yes, trackpads generate wheel events when you swipe with two fingers. The delta values and event frequency will differ from a physical mouse wheel.
What is a good events per second rate?
For a standard notch-based mouse, 5 to 10 events per second is typical during fast scrolling. Smooth-scrolling mice can produce 30 to 60 events per second.
Are my results saved?
No. The scroll test is a real-time diagnostic tool and does not save results. Each session is independent.