Files with the RMX extension are associated with the RealPlayer media player and the RealJukebox media asset management tool. RMX is an audio file that is protected against unauthorized use. This security is based on pairing the file with a specific device (only on that device can play the song) or a digital key owned by the user.

RMX is the format that has been used in RealPlayer since version 10. RealJukebox is now an integral part of RealPlayer.