DivX is a common video format on the internet that cannot be played in Windows without installing a decoder first. This download package from DivX includes a player for web browsers, a standalone player and a converter for watching the videos on other devices.
The web player can play videos in HD. Indeed up to 4K resolution, with 5.1 surround sound. Subtitles can displayed if they are available. The player can save videos if you want to watch them again or transfer them to another player.
Note that DivX is now completely free.