Mouse wheel and trackpad
Scroll Wheel Test
Scroll inside the test area and see every wheel event the browser delivers — direction, deltas and units — without the test hijacking your page scrolling.
Move your mouse over this area and scroll the wheel or swipe the trackpad.
Recent wheel events
No wheel events yet. Each event the browser delivers to this area is listed here, newest first.
How to use
Checking your scroll wheel
Honest limits
Why readings differ between devices
The values you see depend on more than your wheel: trackpads send streams of small pixel deltas, notched mice send larger steps, browser smooth scrolling splits one gesture into many events, and some browsers report lines or pages instead of pixels. Operating system scroll settings (lines per notch, natural direction) change the numbers too.
So treat this page as a live view of what the browser received — useful for confirming direction, horizontal scrolling and event delivery — not as a calibration instrument or a way to diagnose wheel hardware. The area-capture option affects only the dotted zone and can be switched off at any time.
Questions
Scroll wheel test FAQ
What does this scroll wheel test do?
It listens for wheel events inside the marked test area and shows what the browser received: the direction, the deltaX and deltaY values, the deltaMode (pixels, lines or pages), a live list of recent events and counters per direction. It is an observation of the events, not a hardware diagnostic.
How do I test my scroll wheel?
Move your mouse pointer over the dotted test area and scroll. The big arrow shows the direction of the most recent event and the table below lists the latest events with their raw values. Scroll up, down, left and right (if your wheel tilts) to see each direction register.
Why does the page stop scrolling when I scroll inside the area?
While the “Keep scrolling inside this area” option is checked, the test area intercepts wheel events so your scrolling registers without moving the page underneath. The capture applies only inside the dotted area — uncheck the option or move the pointer outside it and the page scrolls normally. Events are recorded either way.
Why do I get many small events for one flick on my trackpad?
Trackpads and smooth-scrolling mice deliver streams of small pixel-based deltas; classic notched mice often send one larger delta per notch, and some browsers convert notches into “line” units. Different devices and browser settings produce very different numbers, so compare readings only against your own previous runs.
What do deltaX and deltaY mean?
deltaY is vertical scrolling: negative scrolls up, positive scrolls down. deltaX is horizontal scrolling: negative left, positive right. The units depend on deltaMode — pixels, lines or pages — which is shown next to every event.
Can this tell me if my scroll wheel is broken?
No. It shows whether the browser received wheel events and what their values were. If nothing appears while you scroll, the events were dropped somewhere between the device, the operating system and the browser — a web page cannot tell where. Use it to observe, not to diagnose hardware.
Does it work on touch screens?
Touch screens do not produce wheel events, so on a touch-only device the counters stay at zero and the page shows a notice. A mouse wheel or a trackpad is required.
Is any of this data sent anywhere?
No. Event values exist only in this page and are cleared when you press Clear or leave. This site has no analytics, so nothing about your scrolling is transmitted — check the network panel if you want to verify.