RMVB (acronym for RealMedia Variable Bitrate) is an enhanced variation of the RM file extension developed by RealNetworks.

As opposed to the somewhat similar RM format, RMVB files are typically encoded at variable bitrates, therefore they are largely used for multimedia content stored locally.

Due to this format's benefits, users often convert files of other formats to RMVB, thus creating custom files.

Furthermore, before actually converting the files, users have the possibility to adjust the source's bit rate, aspect ratio or audio channel according to the user's preferences.