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 :-moz-system-metric(scrollbar-thumb-proportional) CSS pseudo-class will match an element if the computer's user interface uses proportional scrollbar thumbs; that is, the draggable thumb on the scrollbar resizes to indicate the relative size of the visible area of the document.
This selector is intended for use mainly by theme developers.
Note: Since Firefox 58, this pseudo-class is no longer available to web content — it is only available internally (e.g. to XUL / chrome code). See bug 1396066 for more details.
Specifications
Not part of any specification.
Browser compatibility
| Desktop | Mobile | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
:-moz-system-metric(scrollbar-thumb-proportional) | Chrome No support No | Edge No support No | Firefox
No support
3 — 58
| IE No support No | Opera No support No | Safari No support No | WebView Android No support No | Chrome Android No support No | Firefox Android
No support
4 — 58
| Opera Android No support No | Safari iOS No support No | Samsung Internet Android No support No |
Legend
- No support
- No support
- Non-standard. Expect poor cross-browser support.
- Non-standard. Expect poor cross-browser support.
- Deprecated. Not for use in new websites.
- Deprecated. Not for use in new websites.
- See implementation notes.
- See implementation notes.