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mousewheel

Non-standard
This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.

The mousewheel event is fired asynchronously when a mouse wheel or similar device is operated. It's represented by the MouseWheelEvent interface.

Do not use this wheel event.

This interface is non-standard and deprecated. It was used in non-Gecko browsers only. Instead use the standard wheel event.

Interface :MouseWheelEvent
Synchronicity :asynchronous
Bubbles : yes (Though, MSDN documents "No")
Target : Element, Document, Window
Cancelable : yes (Though, MSDN documents "No")
Default action : Scroll, moving history, or zooming in/out

Specification

The document in MSDN: onmousewheel event

Browser compatibility

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Feature	Chrome	Edge	Firefox (Gecko)	Internet Explorer	Opera	Safari
Basic support	1.0	(Yes)	No support	6.0	10.00	3.0
`wheelDeltaX`	1.0	(Yes)	No support	No support	No support	3.0
`wheelDeltaY`	1.0	(Yes)	No support	No support	No support	3.0

Feature	Android	Edge	Firefox Mobile (Gecko)	IE Mobile	Opera Mobile	Safari Mobile
Basic support	?	(Yes)	No support	?	?	?
`wheelDeltaX`	?	(Yes)	No support	?	?	?
`wheelDeltaY`	?	(Yes)	No support	?	?	?

detail value

The detail attribute value is always 0 except Opera (Presto).

Opera (Presto) sets almost the same value as Firefox (Gecko)'s DOMMouseScroll event's detail value which indicates the scroll amount by line. Negative value indicates to scroll to bottom or right. Positive value indicates to scroll to top or left.

On Mac, the value is computed from accelerated scroll amount.

On Linux, 2 or -2 is set per native wheel event.

wheelDelta, wheelDeltaX and wheelDeltaY value

The wheelDelta attribute value is an abstract value which indicates how far the wheel turned. If the wheel has rotated away from the user, it's positive, otherwise negative. This means that the delta value sign is different from DOM Level 3 Event's wheel. However, the meaning of the amount of these values is not the same between browsers. See following explanation for the detail.

IE and Opera (Presto) only support wheelDelta attribute and do not support horizontal scroll.

The wheelDeltaX attribute value indicates the wheelDelta attribute value along the horizontal axis. When a user operates the device for scrolling to right, the value is negative. Otherwise, i.e., if it's to left, the value is positive.

The wheelDeltaY attribute value indicates the wheelDelta attribute value along the vertical axis. The sign of the value is the same as the wheelDelta attribute value.

IE

The value is the same as the delta value of WM_MOUSEWHEEL or WM_MOUSEHWHEEL. It means that if the mouse wheel doesn't support high resolution scroll, the value is 120 per notch. The value isn't changed even if the scroll amount of system settings is page scroll.

Chrome

On Windows, the value is the same as the delta value of WM_MOUSEWHEEL or WM_MOUSEHWHEEL. And also, the value isn't changed even if the scroll amount of system settings is page scroll, i.e., the value is the same as IE on Windows.

On Linux, the value is 120 or -120 per native wheel event. This makes the same behavior as IE and Chrome for Windows.

On Mac, the value is complicated. The value is changed if the device that causes the native wheel event supports continuous scroll.

If the device supports continuous scroll (e.g., trackpad of MacBook or mouse wheel which can be turned smoothly), the value is computed from accelerated scroll amount. In this case, the value is the same as Safari.

If the device does not support continuous scroll (typically, old mouse wheel which cannot be turned smoothly), the value is computed from non-accelerated scroll amount (120 per notch). In this case, the value is different from Safari.

This difference makes a serious issue for web application developers. That is, web developers cannot know if mousewheel event is caused by which device.

See WebInputEventFactory::mouseWheelEvent of the Chromium's source code for the detail.

Safari

The value is always computed from accelerated scroll amount. This is really different from other browsers except Chrome with continuous scroll supported device.

Note: tested with the Windows package, the earliest available version was Safari 3.0 from 2007. It could be that earlier versions (on Mac) support the properties too.

Opera (Presto)

The value is always the detail attribute value ✕ 40.

On Windows, since the detail attribute value is computed from actual scroll amount, the value is different from other browsers except the scroll amount per notch is 3 lines in system settings or a page.

On Linux, the value is 80 or -80 per native wheel event. This is different from other browsers.

On Mac, the detail attribute value is computed from accelerated scroll amout of native event. The value is usually much bigger than Safari's or Chrome's value.