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 ::-ms-fill-lower CSS pseudo-element represents the portion of the "track" (the groove in which the indicator aka thumb slides) of an <input> of type="range", which corresponds to values lower 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 |
::-moz-range-progress
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https://developer.mozilla.org/en-US/docs/Web/CSS/::-ms-fill-lower