A format war describes competition between mutually incompatible proprietary formats, typically for data storage devices and recording formats for electronic media, often forcing content publishers to "take sides" by supporting one format or the other. It typically results from a failure of two or more entities to agree on a technical standard for delivery of the same content. Perhaps the most famous example was the videotape format war of the late 1970s and early 1980s, between the rival VHS and Betamax videotape formats.

Although technical superiority is typically a factor in determining which format "wins", other factors can have a greater, deciding influence. As an example, though LaserDisc offered near-DVD-quality resolution in the 1970s, most consumers still chose the videotape standards which only offered 60% the resolution, but provided the ability to record television programs.

Here are some notable examples of format wars, organized according to when the battle for consumer adoption first started:

1910s

Early recording media formats: cylinder records versus disk records. In 1877 Thomas Edison invented sound recording technology using a tin cylinder record, and soon thereafter mass-marketed the wax "Edison cylinder". In 1886 Berliner invented disk records. By the late 1890s cylinders and disks were widespread. Cylinders were more expensive to manufacture, but any cylinder player could make recordings. Disks saved space and were cheaper, but due to the constant angular velocity (CAV) of their rotation, the sound quality varied noticeably from the long outer edge to the short inner portion nearest the center; and disk record players could not make recordings. Edison, a stickler for sound quality, refused to produce the disks until the late teens, when Berliner's patent expired.

1920s

78 rpm gramophone record formats: lateral versus vertical "hill-and-dale" groove cutting. When Edison finally introduced his "diamond disc" (using a diamond instead of a steel needle), it was cut hill-and-dale, meaning that the groove modulated on the vertical axis as it had on all cylinders - unlike other manufacturers' disks which were cut laterally, meaning that the groove modulated on the horizontal axis. In 1929 Thomas Edison bowed out of the record industry altogether, ceasing all production of his disks, and also cylinders which he had also manufactured up to that point. In addition, there were several more minor "format wars" between the various brands using various speeds ranging from 72 to 96 rpm. The Edison disks rotated at about 80 rpm. In 1958, the stereophonic record was introduced which uses perpendicular modulations for each channel, providing backward compatibility to the lateral-cut monaural recording.

1940s

Vinyl record formats: Columbia Records' 12-inch (30 cm) Long Play (LP) 33⅓ rpm microgroove record versus RCA Victor's 7-inch (17.5 cm) / 45 rpm Extended Play (EP) during the years 1948–1950. Ended in a compromise because each format found a separate marketing niche, and record players were redesigned to use either type. Both formats nearly disappeared with the rise of the Compact Disc, though vinyl records are still used by niche audiences such as disk jockeys and audiophiles. Also, many newer albums have seen special limited edition releases on LP format.

1960s

Portable audio formats: 8-track and four-track cartridges vs. Compact Cassette. While notably successful into the mid-to-late 1970s, the 8-track eventually lost due to technical boundaries, including variable audio quality and lack of fine control.

FM radio broadcast formats: The Crosby system and the GE/Zenith system. The Crosby system was technically superior, particularly in transmitting clear stereo signals, due to its use of an FM subcarrier for stereo sound instead of the AM subcarrier employed by GE/Zenith. Many radios built in this period allowed the user to select Crosby or GE/Zenith listening modes. However the Crosby system was incompatible with lucrative SCA services such as in-store broadcasting and background music. FM station owners successfully lobbied the FCC to adopt the GE/Zenith system in 1961, which was SCA-compatible.

1970s

Various Quadraphonic encoding methods: CD-4, SQ, QS-Matrix, and others. The expense (and speaker placement troubles) of quadraphonic, coupled with the competing formats requiring various demodulators and decoders led to an early demise of quadraphonic, though 8-track tape experienced a temporary boost from the introduction of the Q8 form of 8-track cartridge. Quadraphonic sound returned in the 1990s substantially updated as surround sound but incompatible with old hardware.

VHS vs. Betamax vs. Video 2000, the Video Tape Format War. The war started in 1976 and by 1980, VHS controlled 70% of the North American market. By 1984, forty companies utilized the VHS format in comparison with Beta's twelve.

Capacitance Electronic Disc (CED) vs. LaserDisc (LD) vs. VHD (Video High-Density), non-recordable video disc formats. All of these ultimately failed to achieve widespread acceptance, although LD found a small videophile market that appreciated its near-DVD quality images, and sustained it until the arrival of DVDs. The majority of consumers preferred the recordable videotape for capturing live television and later home movies,thereforemaking VHS standard in consumers' homes (see videotape format war).

Vinyl record vs. Compact Cassette - The popular 33-1/3 record dominated most of the 20th century, from the 1940s to the 1980s until newer technologies supplanted it. Its main rival the compact cassette was slow in growth but with the advent of boomboxes and Walkmans in the 70s and early 80s, cassettes eventually outsold vinyl records in the 1980s. Cassettes provided convenient mobile operation, playback free of scratches or skips, and near-CD quality on Type II pre-recorded music encoded with Dolby B. (See also Vinyl record vs. CD.)

1980s

Home computers typically with very similar overall capabilities, sometimes even within the same microprocessor, often had incompatible peripherals such as joysticks, printers, or data recording (tape or disk). Vast incompatibilities could exist even within a company's product line, sacrificing backward compatibility. For example if a C64 user wanted a printer, he could not buy a product from Atari or IBM or Apple. He would need to buy a Commodore-made printer (or else risk not all programs working with a non-compatible device). Gradually computer & game systems standardized on "Atari 2600 connectors" for joysticks and mice (during the 1980s), parallel port for printers (mid-80s), the MS-DOS-derived FAT12 format for floppy disks (mid-90s), and so on. The main standards used on today's 2008 computers are HFS, Ext3, FAT32, or NTFS.

AM stereo was capable of fidelity almost as good as FM but was doomed in the USA by competing formats during the 1980s with Motorola's C-QUAM competing vigorously with three other incompatible formats including those by Magnavox, Kahn/Hazeltine, and Harris. It is still widely used in Japan, Canada, and Australia, but only sees sporadic use in the United States despite the fact most AM radios support stereo capability .

Video8 vs. VHS-C and later Hi8 vs. S-VHS-C tape formats (see camcorder). This is an extension of the VHS vs. Betamax format war, but here neither format "won" widespread acceptance. Video8 had the advantage in terms of recording time (4 hours versus 2 hours maximum), but consumers also liked VHS-C since it could easily play in their home VCRs,thereforethe two formats essentially split the camcorder market in half. As of 2007, JVC still makes VHS-C and S-VHS-C camcorders; Sony announced its last Hi8 camcorder- the TRV238.

Compact Cassette vs. CD - Although 1980s-era portable CD players challenged cassettes, early players had problems with skipping due to vibrations & shock, which was unsatisfactory to the consumer and allowed cassettes to continue to dominate. It was not until the 1990s with the arrival of new "skip-free" technology (where the CD player uses memory buffering to read-ahead on the disc) that CD sales eclipsed cassettes both at home and "on the go". Consumers preferred the CD's convenience, superior sound, and seemingly indestructible format (no more scratched records or tangled tapes). CDs are still the main method of pre-recorded distribution in the 2000s, although downloadable audio files are slowly eroding that dominance.

1990s

Digital Audio Tape (DAT) by Sony vs. Digital Compact Cassette (DCC) by Philips vs. MiniDisc (MD) by Sony, won by neither. Since CDs at the time (late 80s/early 90s) were play-only, these recordable tape formats were an attempt to bring CD-quality recording to home consumer. Restrictions by record companies fearful of perfect digital copies led to very restrictive recording,thereforehandicapping both technologies. Ultimately the consumers chose neither format, preferring to stick with analog Compact Cassettes for home audio recording, and eventually upgrading to CD recordable discs and lossy-compressed MP3 formats.

X2 vs K56flex – In the race to achieve faster telephone line modem speeds from the then-standard 9.6 kbit/s, many companies developed proprietary formats such as V32.terbo (19.2 kbit/s) or TrailBlazer (23.0 kbit/s) or V.FAST (28.8 kbit/s), hoping to gain an edge on the competition. The X2 and K56flex formats were a continuation of that ongoing battle for market dominance until the V.90 standard (based on K56flex, but not identical) was developed in 1999. For some time, online providers needed to maintain two modem banks to give dial-up access for both technologies. (See "modem" for a complete history.)

Digital video formats: DVD versus DIVX (not to be mixed up with DivX). DIVX was similar to DVD, but was cheaper (about four dollars) and could only be viewed for 48 hours after their first use. DIVX players could play DVDs, but standard DVD players couldn't play DIVX disks. Several Hollywood studios (Disney, 20th Century Fox, and Paramount Pictures) initially released their movies exclusively in the DIVX format, but the same features that caused them to support it (namely, the pay-per-view features) caused consumers to ultimately support DVD.

Memory cards, a four-way contest: CompactFlash vs. Memory Stick vs. MultiMediaCard / Secure Digital card vs. SmartMedia. The format war became a five-way contest with the introduction of xD-Picture Card in the next decade, although by then SmartMedia was falling into disuse. This ongoing contest is complicated by the existence of multiple variants of the various formats. Some of these, such as miniSD, are compatible with their parent formats, while current generations of Memory Sticks break compatibility with the original format.

Hi-fi digital audio discs: DVD-Audio versus SACD. These two formats are likely to coexist due to newer players that handle both formats with equal ease (although most such devices are exclusively PCM-based and do not truly support SACD's PDM system), though neither caught on with the market, many feel this was specifically due to the format war that DVD-video avoided. The fastest-growing music formats today are heavily lossy compressed formats.

2000s

Recordable DVD formats: DVD+R versus DVD-R, and originally DVD-RAM. Ultimately this has been resolved, as most new DVD recorders support both formats designated with DVD±R.

Digital audio data compression formats: MP3 versus Ogg Vorbis versus Advanced Audio Coding versus Windows Media Audio. As with digital video, the competing formats can be played on the same equipment (with the exception of some mobile players). Each format has found its own niche - while MP3 is the de facto standard for audio encoding, AAC is favored by commercial music distributors, and Vorbis has found its strongest use among game developers and the like who have need for a high-quality audio codec but do not want to pay the licensing fees attached to other codecs.

Digital video data compression formats: Windows Media Video versus RealVideo versus DivX versus QuickTime versus Ogg Theora. While in theory, all formats work equally well on most major operating systems like Microsoft Windows, which makes the stakes for the consumer considerably lower, support for WMV, based on ASF, is not typically included by default with free software operating systems and players due to legal issues (with that said, end-user installable software packages are readily available to address these shortcomings, although they exist in somewhat of a legal grey area: see MPlayer). According to the popular site Doom9, DivX video codec boasts the highest quality versus compression rate of those already mentioned, while it is beaten by Xvid, which is bested by x264.

High-definition optical disc formats: Blu-ray Disc versus HD DVD. The first HD DVD player was released in March 2006, with the first Blu-ray player following in June 2006. In addition to the standalone players for each format, Sony's PlayStation 3 is a Blu-Ray player and its games use that format as well. Microsoft's Xbox 360 is a DVD player, and also offers consumers an optional HD DVD external player, but the games continue to use the standard DVD format.

Ultra-wideband networking technology - in early 2006, an IEEE standards working group disbanded because two factions could not agree on a single standard for a successor to Wi-Fi. (WiMedia Alliance, IEEE 802.15, WirelessHD)