A format war describes competition between competing media formats, usually very costly to the format-owning parties involved. Perhaps the most famous example was the videotape format war of the late 1970s / early 1980s, between the rival VHS and Betamax Videotape formats.

Other examples include the following:

• High-definition DVD formats: Blu-ray versus HD-DVD versus Enhanced Versatile Disc
• Recordable DVD formats: DVD+R versus DVD-R, and originally DVD-RAM
• Video game formats: cartridges, championed by Nintendo versus CDs used by Sony and Sega
• Digital video data compression formats: Windows Media Video versus RealVideo versus DivX versus QuickTime. However, all formats work equally well on most major operating systems (OS's) like Microsoft Windows, which makes the stakes for the consumer considerably lower.
• Digital audio data compression formats: MP3 versus Ogg Vorbis versus Advanced Audio Coding versus Windows Media Audio. As with digital video, the competing formats work equally well on most OS's.
• Hi-fi digital audio discs: DVD-Audio versus SACD
• AM stereo was capable of even higher fidelity than FM but was doomed in the USA by competing formats during the 1980s with Motorola's C-QUAM fighting it out with four other incompatible formats including those by Magnavox, Kahn /Haseltine, and Harris.
• Portable audio tape formats: 8-track and four-track cartridges versus Compact audio cassette
• Vinyl record formats: Columbia Record's 12-inch (30 cm) Long Play (EP) 33⅓ rpm microgroove record versus RCA Victor's 7" (17.5 cm) / 45 rpm Extended Play (EP) during the years 1948-1950.