The WheelEvent.deltaMode read-only property returns an unsigned long representing the unit of the delta values scroll amount. Permitted values are: Constant Value Description DOM_DELTA_PIXEL 0x00 The delta values are specified in pixels. DOM_DELTA_LINE 0x01 The delta values are specified in lines. DOM_DELTA_PAGE 0x02 The delta values are specified in pages. Syntax var unit = event.deltaMode; Example var syntheticEvent = new WheelEvent("syntheticWheel", {"deltaX": 4, "deltaMode": 0}); console.log(syntheticEvent.deltaMode); Specifications Specification Status Comment Document Object Model (DOM) Level 3 Events SpecificationThe definition of 'WheelEvent.deltaMode' in that specification. Obsolete Initial definition. Browser compatibility Desktop Mobile Feature Chrome Edge Firefox (Gecko) Internet Explorer Opera Safari (WebKit) Basic support 31 (Yes) 17.0 (17.0) 9.0 18 7.0 Feature Android Edge Firefox Mobile (Gecko) IE Phone Opera Mobile Safari Mobile Basic support (Yes) (Yes) 17.0 (17.0) ? (Yes) No support See also wheel WheelEvent