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.
::-ms-fill-upper CSS pseudo-element represents the portion of the "track" (the groove in which the indicator aka thumb slides) of an
type="range", which corresponds to values greater than the value currently selected by the thumb.
Not part of any specification.
Microsoft has a description on MSDN.
|Feature||Firefox (Gecko)||Chrome||Edge||Internet Explorer||Opera||Safari|
|Basic support||No support||No support||(Yes)||(Yes)||No support||No support|
|Feature||Firefox Mobile (Gecko)||Android||Edge||IE Phone||Opera Mobile||Safari Mobile|
|Basic support||No support||No support||(Yes)||?||No support||No support|