a compressed audio format created in 1995 by Progressive Networks, which became RealNetworks, Inc., in 1997.

The RealAudio format allows users to listen to music as it is being downloaded, a process known as streaming. RealAudio's small file sizes and streaming capability make it a popular format for Internet radio stations. RealAudio was developed for use with RealPlayer, one of the Internet's early media player successes.

RealNetworks established new proprietary file types, such as .rm and .ra, to go along with their RealPlayer technology; while the company's competitors developed their media players to play established file types, such as .avi and .mpg. One of RealAudio's drawbacks has been the reluctance of RealNetworks to provide information and computer code that could allow for third-party creations and alterations of the company's products. Although this stance has softened somewhat, RealNetworks has long preferred to maintain exclusive control over all things related to RealPlayer and its media. The Helix Community was created by RealNetworks to attempt to reach out to their open-source (open source) community, but Helix's player cannot play all RealAudio files. In 2003 RealNetworks purchased Rhapsody, an online music store, and renamed it RealRhapsody.

In December 2003 RealNetworks began a legal battle with the Microsoft Corporation over complaints that Microsoft was using its dominance of the personal computer market to redirect customers to its Windows Media Player. In 2005 Microsoft settled by paying RealNetworks $761 million.