There is only one file type that uses the .KUX extension:
Youku KUX Video
A KUX file is a video downloaded from Youku, a Chinese online video-sharing platform. It contains a video that had been posted to Youku before being downloaded and saved using the platform's associated desktop or mobile applications. KUX files can be played using the Youku desktop and mobile applications, and they can be converted to more common video formats using FFmpeg.
Youku, which is China's answer to YouTube, allows users to download most videos that have been posted to the platform, using the platform's associated desktop and mobile applications. When users download a Youku video, the video is saved as a KUX file.
KUX files are similar to .FLV files, but contain a unique header designed to make the files playable only in Youku's video players. However, the developers behind FFmpeg have added support for the KUX format, allowing users to convert KUX files to more common video formats and play them in other media players.
If you have already downloaded and installed Youku's desktop or mobile applications, you can open and play KUX files in those apps. If you do not want to install Youku on your computer or mobile device, you can convert a KUX file to a more common video format using FFmpeg. Then, you can play the converted file in the media player of your choice.
Updated: March 15, 2021