RealMedia is a proprietary multimedia container format created by RealNetworks. Its extension is ".rm". It is typically used in conjunction with RealVideo and RealAudio and is used for streaming content over the Internet. Typically these streams are in CBR (constant bitrate), but a container for VBR (variable bitrate) streams, named RMVB (RealMedia variable bitrate), has been developed.
Support of RealMedia is available in a few multimedia players for different architectures/platforms, including RealPlayer and the Real Alternative codec pack. The open-source DAP firmware Rockbox has added support for reading RM containers as of 6 July 2009, although only certain formats used in RM files are playable.