Real Video is produced by Real Networks and a free viewer is available from the Real Player web site. The Real Player is available for the following platforms: Windows 3.1, 95, NT; MacOS 7, 8; OS/2, Linux, Solaris, SunOS, Irix, FreeBSD.
Quicktime has been developed by Apple and is available from the Apple Quicktime web site. The Quicktime Player is available for the following platforms: Windows 3.1, 95, NT; MacOS 7, 8.
Other plug-ins for audio and video format are available and may play either of these formats too. For a wider range of plug-ins, try Netscape's audio and video plug-ins page.