CSS -moz-opacity, -ms-filter, -khtml-opacity

I recently stumbled upon the use of this CSS element in some older code and document it here for future reference.

  • Gecko 1.9.1 (Firefox 3.5 – final release of June 30, 2009) and later do not support -moz-opacity. By now, you should be using simply opacity.
  • Prior to version 9, Internet Explorer does not support opacity, rather it supports filter instead.
  • IE supports also the extended form progid:DXImageTransform.Microsoft.Alpha(Opacity=xx).
  • IE8 introduced -ms-filter, which is synonymous with filter.
  • Similar to -moz-opacity, -khtml-opacity has been dead since early 2004 (release of Safari 1.2).
    Konqueror never had support for -khtml-opacity and had been supporting opacity since version 4.0.