File Types
A file's extension is the shortest history lesson on a computer. Three or four letters after a dot say which company or committee made the format, which machine it was made for, roughly what year, and what people were doing with pictures, video and sound at the time. This page reads that history out of the extensions a collection accumulates: from the bulletin boards and CD-ROMs of the late 1980s, through the dial-up web, Napster and DivX, to the phones, Discord and Reddit of today.
It is for a reader with a drive full of these who wonders what half of them are. Each section says where a format came from, who made it and for which machine, what it was made to do, and how it found its footing with the people who used it, and links to the specification, the announcement or the account that tells the longer story. It is not a reference to any one program's abilities, and it does not say what will open a file today; that changes, and the history does not. Fuji's settings panel carries a shorter version of each entry below, a few sentences on the card of every kind of file in its table.
The formats fall into four rooms: pictures, video, sound, and the small text files that sit beside the media and tell a player what to do with it. Within each room they run roughly in the order a collector met them.
Pictures
BMP and DIB, Windows' own bitmap
Microsoft's bitmap came from Windows 2.0 and OS/2 in the late 1980s, when Windows adopted OS/2's bitmap layout so the two could trade pictures, and it took the form most files still carry with Windows 3.0 in 1990, built around a forty-byte header. A BMP stores every pixel as the display would show it, a row at a time from the bottom up, and compresses nothing unless asked, so a 1024 by 768 wallpaper at 24 bits is 2.3 megabytes whatever is in it. That simplicity was the design: Microsoft's own description of the file is a file header, an information header, a color table and the pixels, and any program on any machine can read one with a page of code.
Windows wrote it everywhere. The wallpaper tiles that shipped with Windows 3.1 and 95 were BMPs, every picture Paint saved was one until Windows 7 made PNG its default, and the screenshot the Print Screen key put on the clipboard was a bitmap. It never carried on the web, where its size ruled it out and every byte crossed a modem, and a BMP today most often comes from a scanner's own software or a program of that decade.
.dib is the device-independent bitmap, Windows 3.0's name in 1990 for a picture stored by its own pixels rather than a display adapter's, and that is what every BMP has been since. The name turned up as a file extension when a few of Windows' own tools and some others saved with it, and a .dib is a BMP inside, now and then missing the fourteen-byte file header a .bmp begins with.
PCX, the picture format of DOS
Before Windows had a bitmap, the PC's picture format was ZSoft's. PC Paintbrush was the DOS paint program of 1984, and its PiCture eXchange format, from 1985, was what it saved: up to 256 colors from a palette, run-length compressed, which suited the flat-colored screens of the day. Microsoft licensed Paintbrush as the paint program of Windows 3.0 in 1990, so every Windows machine wrote PCX, and scanners, the clip-art collections sold on floppy and CD, and the games of the early 1990s kept their artwork in it.
That palette was its limit when true color arrived. Windows 95 replaced Paintbrush with Paint, GIF and JPEG took the rest, and a PCX today is a picture that has been sitting on a drive since the first half of the 1990s.
GIF
CompuServe was an online service before there was a public internet, and in June 1987 it needed a picture format its subscribers could trade over a modem and see on any of the incompatible computers of the day. The Graphics Interchange Format was the answer, and its specification still says what it was for: "a protocol intended for the on-line transmission and interchange of raster graphic data in a way that is independent of the hardware used in their creation or display." A frame holds 256 colors from a palette, and the 89a revision of 1989 added transparency, all or nothing, and the frame delays that make an animation.
The web took it up in its first year. In February 1993 Marc Andreessen, writing the Mosaic browser at the University of Illinois, sent a short message to the mailing list where the web's first programmers talked:
I'd like to propose a new, optional HTML tag:
IMG
Required argument is SRC="url". This names a bitmap or pixmap file for the browser to attempt to pull over the network and interpret as an image, to be embedded in the text at the point of the tag's occurrence.
Mosaic shipped the tag that year, GIF was the format it showed, and for the first years of the web GIF was the only picture every browser drew: the logos, the buttons, the blinking "under construction" signs, and in the 2000s the reaction loops, since a few seconds of looping video in a GIF played in every browser, forum and phone without a plugin, at the cost of megabytes.
The compression inside it was somebody else's. LZW had been Unisys's patent since 1985, and in the last days of December 1994 CompuServe and Unisys announced that developers of software writing GIFs would pay a royalty. The League for Programming Freedom's account of the announcement catches the mood of the week: the patent holders had "decided to try to make money off the fact that the Internet has recently started resembling a marketplace." The patent expired in the United States in June 2003 and in Europe a year later, and by then the web had two picture formats.
JPEG, in four spellings
The Joint Photographic Experts Group drafted its standard from 1986 and published it in 1992, as ITU recommendation T.81. It shrinks a photograph to a tenth of its size by discarding the fine color detail the eye least notices, in blocks of 8 by 8 pixels, and it was the picture of the web from Mosaic on and of every digital camera from the late 1990s to the phone in a pocket today. The loss shows as a halo around sharp edges and text, and it compounds each time a picture is edited and saved again. It holds no transparency.
The standard said how to compress a picture and not how to store one in a file. In late 1991 Eric Hamilton of C-Cube Microsystems gathered about forty representatives of computer, telecommunications and imaging companies at C-Cube, and the result, the JPEG File Interchange Format, version 1.02 of September 1992, is the layout almost every JPEG follows inside, whatever it is called.
The four spellings are the history of file names. .jpg is JPEG cut to three letters to fit DOS's eight-and-three file names, and it became the common spelling because that is where most people made their files. .jpeg is the four-letter spelling of the Mac and Unix, which never had the limit, and of the web's own tools and many phones since; the spelling tells where a file came from and nothing more. .jpe is the rarest three-letter cut, which a few programs of the 1990s wrote and the MIME registries still list beside the other two. Nothing writes it now.
.jfif names the layout rather than the compression, and it was almost unknown as an extension until a Windows 10 update in 2017 mapped the image/jpeg type to .jfif in the registry, under a key the browsers consult when they save a picture. Firefox and Chrome on Windows then saved pictures from Twitter and elsewhere under that name for about three years, to the bafflement of everyone who found them, and the complaint reached Mozilla's bug tracker in 2020 with the registry key named. Inside, all four are the same file.
PNG
The Portable Network Graphics format was designed on a mailing list in the first weeks of 1995, in direct answer to the royalty announcement of the week before. The libpng project's own history keeps the dates: Thomas Boutell posted a first draft, called PBF, to three Usenet groups on January 4; an informal working group formed around it; the name became PNG on January 23; the specification was frozen on March 7; and working libraries shipped on May 1. The specification, which says the name is "pronounced 'ping'", became a W3C recommendation in October 1996.
The design was better than the format it replaced. PNG holds 16 million colors with an alpha channel, so transparency can be smooth rather than all or nothing, it compresses with the same deflate as a zip file, and it loses nothing. Browsers on Windows were the holdout: Internet Explorer drew alpha transparency wrong until version 7 fixed it in 2006, so for a decade web designers made GIFs they would rather have made PNGs. From then it was the format of screenshots, logos, icons and every interface graphic, and the one Paint has saved by default since Windows 7. A photograph saved as PNG comes out several times larger than as JPEG, which is the one job it is wrong for.
SVG
Scalable Vector Graphics describes a picture as shapes rather than pixels, in XML, so a logo is a few hundred bytes and stays sharp at any size. It was drawn up after two camps had each proposed a vector format for the web in 1998 and neither won: PGML, from Adobe, IBM, Netscape and Sun, and VML, from Microsoft, Macromedia, Autodesk, Hewlett-Packard and Visio. The W3C's own format took from both and became a recommendation on September 4, 2001.
Internet Explorer refused it for a decade while Adobe shipped a plug-in, and only when Internet Explorer 9 drew it in March 2011 did it become the web's format for icons, logos, charts and diagrams. Today two websites in three serve one, by W3Techs' count for October 2026. It has no way to hold a photograph.
WebP
Google bought On2 Technologies in 2010 for its VP8 video codec, and on September 30 of that year announced a picture format cut from it: a WebP is one VP8 frame, and the announcement said it "promises to significantly reduce the byte size of photos on the web," claiming an average 39 percent reduction over a million pictures pulled from the web. Google's own later comparison put a WebP at 25 to 34 percent smaller than a JPEG of the same quality, and that was the pitch: a faster web. A lossless mode, transparency and animation followed by 2012.
Chrome showed it from the start, and for most of the decade little else did: a picture saved from a Google property would not open in most programs, and collectors remember the format that way. Firefox took it in 2019 and Safari in 2020, and a fifth of websites serve it now, which makes it the second commonest picture the web hands over.
AVIF
The Alliance for Open Media is the group Google, Netflix, Mozilla, Amazon and Microsoft formed to make a video codec free of royalties, and the AV1 Image File Format, published in 2019, is one intra frame of that codec stored in the HEIF container. A picture is about half a JPEG's size at the same quality, with high dynamic range, wide color and transparency. Chrome drew it from version 85 in 2020, Firefox from 93 in 2021, Safari from 16.1 in 2022 and Edge from 121 in 2024, and the services that resize the web's pictures send it to browsers that ask, though it is still under two percent of websites. Encoding one takes several times as long as a JPEG.
HEIC and HEIF
The High Efficiency Image File Format is MPEG's container for pictures, finalized in 2015 and published in 2017, and .heic is Apple's name for a HEIF file holding HEVC pictures. Every iPhone has shot in it by default since iOS 11 and the iPhone 7 in 2017, which Apple introduced to developers that June, and many Android phones since. A picture is one intra frame of HEVC video, about half a JPEG's size at the same quality, with room for wide color, a depth map and a burst in one file. It is the camera roll of a billion phones, and a PC opens one only with two extensions from the Microsoft Store, one of them sold for a dollar, so a phone converts to JPEG when a picture leaves by mail or the web.
.heif is the container's own extension. Apple never writes the name, and though Samsung, Canon and Sony cameras can shoot HEIF, they save it as .heic or .hif, so a .heif file comes from a converter or a tool. Inside is usually the same HEVC still a .heic holds, though the container can also carry AV1 or JPEG.
Targa
Truevision's format is older than most of what surrounds it and more capable than its age suggests. AT&T's EPICenter, an internal venture that became Truevision in a 1987 buyout, defined it in 1984 for its TARGA boards, among the first cards to put a true-color video frame on a PC, which is why a TGA held 24-bit color and an alpha channel when every other PC picture was a palette; the Library of Congress notes that it had 24-bit color before TIFF did. It was the file of broadcast graphics and 3D rendering through the 1990s, and the texture and screenshot format of the id Software games at the decade's end, and 3D tools still write it. A file is simple, usually uncompressed, and large.
TIFF, in two spellings
Aldus published the Tagged Image File Format in the autumn of 1986 so the first desktop scanners had one file to write for PageMaker, and Adobe has owned it since it bought Aldus in 1994. It is the format of the scanner, the fax machine, the print shop and the archive, lossless as a rule and often tens of megabytes. Inside is a list of tags rather than one layout, so a file can hold several pages, or a compression the reading program never learned, and TIFF readers have a long habit of refusing each other's files. The 6.0 specification of June 1992 is still the one.
.tif is the three-letter spelling DOS needed. .tiff is the four-letter one of the Mac and Unix, and the one Apple's own software writes, Preview and the scanner driver among them. Inside they are the same file.
PICT and PCT
The Macintosh of 1984 drew its screen with QuickDraw, and a PICT was a recording of QuickDraw's drawing calls, so a file is lines, shapes and text as well as bitmaps. It was the clipboard format of the classic Mac OS for sixteen years, where a cut from MacDraw pasted into MacWrite as a PICT, and version 2 brought color with the Macintosh II in 1987. Apple's old documentation of the drawing model it recorded is still online, marked obsolete. Mac OS X built its drawing on PDF instead in 2001, and Apple's own programs stopped writing it over the following decade.
.pct is the three-letter spelling, used wherever a name had to fit DOS, so it is the form a Mac picture took on a PC floppy or a clip-art CD of the 1990s.
IFF and LBM, Deluxe Paint's picture
Jerry Morrison of Electronic Arts wrote the EA IFF 85 standard in January 1985 as a general way to build a file from tagged chunks, for the Amiga, and released it to the public domain. Its introduction says what it was for:
Imagine scanning in images of "player" shapes, transferring them to an image enhancement package, moving them to a paint program for touch up, then incorporating them into a game. Or writing a theme song with a Macintosh score editor and incorporating it into an Amiga game. The data must at times be transformed, clipped, filled out, and moved across machine kinds.
Its picture form, ILBM, the interleaved bitmap, was the file Deluxe Paint saved, and every Amiga picture passed through it: the game artwork drawn in Deluxe Paint from its release in November 1985, the demo scene's screens, and the 4096-color HAM pictures the Amiga alone could show. A file holds a palette of up to 256 colors, or the Amiga's own modes with more, stored as bitplanes, which suited the Amiga's hardware and nobody else's.
.lbm is the DOS spelling, from the PC version of Deluxe Paint that Electronic Arts shipped in 1988, which became the paint program of the game industry: the artists at LucasArts and id drew in it, so the backgrounds and sprites of the early 1990s were .lbm files before they were anything else, and some collections keep them that way. The idea outlived the format. RIFF, the structure of WAV and AVI, is Microsoft and IBM's version of IFF, and AIFF, the Mac's sound file, is Apple's.
WMF and EMF, the Windows Metafile
A Windows Metafile is a recording of GDI's drawing calls, from Windows 3.0 in 1990, so a picture is lines and shapes that scale, or a bitmap, or both: the PC's answer to the Mac's PICT. The Enhanced Metafile came with Windows NT 3.1 in 1993, the same recording with 32-bit coordinates and the device independence the old one lacked. They were the format of clip art, the thousands of drawings on the CDs sold in the 1990s and in the gallery inside Office, which still pastes a drawing between its programs as an EMF.
In December 2005 a crafted WMF could run code on any Windows machine that displayed it, through a record meant for printers, and Microsoft's fix that January, bulletin MS06-001, repaired no bounds check: it "removes the support for the SETABORTPROC record type from the META_ESCAPE record in a WMF image."
PSD
Photoshop's document dates from the program's first release, for the Macintosh on February 19, 1990. Thomas Knoll had written it as a program called Display in 1987, Adobe licensed it in 1989, and when the Computer History Museum published the source code of version 1.0.1 in 2013, Knoll said: "For version 1, I was the only engineer." Layers arrived with version 3.0 in September 1994, and a PSD holds the working picture: the layers, the masks, the text still editable and the adjustments not yet applied, so a file is many times a JPEG's size and only Photoshop shows all of it. Adobe's specification describes a flattened composite Photoshop writes in the last section of the file, which is all any other program shows of one. Designers work in it, and the templates and mockups of thirty years are shared in it.
Camera raw: DNG, CR2, NEF and ARW
A digital camera's sensor records more than a JPEG can hold, and a raw file holds the sensor's readings before a picture has been made of them, so exposure and color are still to be decided. Every maker invented its own, and most are TIFF-like structures that outsiders have reverse-engineered rather than read from a specification. Nikon's Electronic Format, .nef, is the raw file of every Nikon digital camera since the D1 of 1999, the first digital SLR a camera maker designed from the ground up rather than fitting a sensor into a film body. Canon's .cr2 ran from the EOS-1D Mark II of 2004 to 2018, when CR3 replaced it, and each new model changed it a little, so the raw converters trailed every camera by months. Sony's .arw is from the Alpha line that began with the α100 in 2006, after Konica Minolta handed its camera business to Sony, and that Sony's mirrorless cameras carried to the top of the market in the 2010s.
Adobe's Digital Negative set out to end that. DNG, published on September 27, 2004, is an open raw format built on TIFF, and Adobe's free converter turns any maker's raw into it. Leica and Pentax wrote it in their cameras, Android has offered it since version 5, Samsung phones since the Galaxy S6 and iPhones in ProRAW since 2020, every one of them opt-in, and most camera makers kept their own formats anyway.
Video
Video on a personal computer is younger than sound or pictures, and the reason is arithmetic: a second of uncompressed standard-definition video is about twenty megabytes, and a 1991 hard drive held forty. Every format below is an answer to that arithmetic, and the answers changed as the drives and the networks did. The container, which is the file's shape, and the codec, which is how the pictures are squeezed, are separate things, and most of the trouble a collector has with old video is a familiar container holding a codec from another decade.
QuickTime: MOV and QT
Apple shipped QuickTime 1.0 on December 2, 1991, and it played a postage-stamp video on a Macintosh and showed what a personal computer could do. The file it defined was a container of tracks, video, sound and text, each with its own timing, and it was flexible enough that MPEG chose it as the base of MP4. On February 11, 1998 Apple and five other companies announced the choice:
Apple Computer Inc., IBM, Netscape Corp., Oracle Corp., Silicon Graphics Inc. and Sun Microsystems Inc. today announced that the International Standards Organization (ISO) has adopted the companies' joint proposal to use Apple's QuickTime File Format as the starting point for the development of a unified digital media storage format for the MPEG-4 specification. The six companies now look forward to collaborating with other companies and industry bodies to further refine the specification and QuickTime file format–ensuring that MPEG-4 quickly gains market acceptance.
Every iPhone records into a .mov, as do many cameras, most often H.264 or HEVC with AAC sound, so inside a recent one is what an MP4 holds under another name. A .mov from the 1990s can hold Cinepak, Apple Video or Sorenson video, which a Mac stopped playing in 2019, when Apple removed the 32-bit QuickTime 7 framework beneath them; Howard Oakley's account of that spring lists the codecs that went, Cinepak, several Sorensons, Flash Video and RealVideo among them, and carries the advice that "now is the time to convert those to formats which will be supported in macOS 10.15." .qt is the earliest spelling, from the Mac of 1991, before .mov became the habit, and the CD-ROMs and Mac collections of the early 1990s carry them.
MP4, M4V, 3GP and 3G2
MPEG-4 Part 14, published in 2003, is the QuickTime container made a standard. It holds video, most often H.264 or its successor HEVC, sound, most often AAC, and subtitles and chapters beside them, with an index that lets a player start anywhere, and it became the one video file nearly everything writes and plays: phones, cameras, the downloads from every video site and the web's own video tag, which every browser plays in its H.264 form. The container is simple and free, and the codecs inside carry patent licenses, so a recent phone's file may hold HEVC, which Windows 10 decodes only with an extension from the Microsoft Store.
Three relatives share the container. .m4v is Apple's name for an MP4 of video, from October 12, 2005, when the iTunes Store began selling music videos and television episodes for the video iPod: "Music videos and short films are $1.99 (US) each, and television shows are $1.99 (US) per episode." Inside it is an ordinary MP4, H.264 with AAC sound, unless it was bought from the store, in which case FairPlay locks it to Apple's software on an authorized machine. HandBrake named its rips .m4v whenever they carried chapters or Dolby sound, which most did, so a .m4v is as likely a DVD rip as a purchase.
.3gp is the video of the phones before smartphones, defined by the 3GPP standards group for the networks of 2003: an MP4 cut down for a flip phone's camera and its data plan, with H.263 or MPEG-4 video and AMR speech-quality sound. Most clips shot on a phone between about 2003 and 2010 are one, at 176 by 144 pixels and a few seconds long, sent by MMS or pulled off by cable. .3g2 is the 3GPP2 twin for the phones on CDMA networks, Verizon and Sprint in the United States, with QCELP or EVRC speech codecs in place of AMR.
AVI and DivX
Microsoft's answer to QuickTime was Video for Windows, in November 1992, and its file was the Audio Video Interleave: a RIFF file interleaving each frame of video with the sound that goes with it, so a CD-ROM drive could play it without seeking. The first release came with Microsoft's own Video 1 and Intel's Indeo, and Cinepak arrived in 1993. It was the first video most PC users ever saw, 160 by 120 pixels stuttering off a CD-ROM encyclopedia.
The container's second life began in 1999, when a French graphic designer, Jérôme Rota, could not play his portfolio after Microsoft changed its MPEG-4 codec, and with a friend cracked the old one to write AVI files instead of ASF. The result, DivX 😉 3.11 Alpha, put a DVD's film into an AVI that fit on a CD, and with broadband arriving it became the box films were traded in, so an AVI from that decade is often a whole film at 700 megabytes, the size of a CD-R. The company that formed around it in 2000 wrote a clean codec from scratch, an open-source fork of that became Xvid, and .divx is the name the company's own tools wrote from DivX 6 in 2005; most DivX films kept the .avi name, and the DVD players of the mid-2000s with a DivX logo on the front played both from a burned disc.
What is inside an AVI depends on the year: Cinepak, Indeo and Microsoft Video 1 in the CD-ROM years, Microsoft's own MPEG-4 and then DivX and Xvid after 1999, and H.264 in a few from the 2010s. It is a box that can hold any codec at all.
MPEG-1 and MPEG-2: MPG, MPEG, MPE, DAT and VOB
The Moving Picture Experts Group's first standard was published in August 1993, and it was the first video format that was truly a standard, so a file from one machine played on any other with the decoder. The group sized it for the 1.5 megabits a second a single-speed CD-ROM delivered, at 352 by 240, and that is what it looks like. It is the video of the Video CD, of the first digital cameras that shot movies, and of the clips traded on CD-ROM and posted on the websites of the early 2000s as a link to a file, saved with a right-click. MPEG-2, 1995, raised the resolution and the bitrate for DVD and digital television, and the two share their extensions. .mpg is DOS's three letters and the common one, .mpeg the four-letter spelling of the Mac, Unix and the web, and .mpe a third, rarer cut from the Unix tools and web servers of the 1990s.
Two more are what the discs look like copied to a drive. Video CD, the standard Philips, Sony, Matsushita and JVC published in 1993, stores its film in an MPEGAV folder as .dat files, an MPEG-1 stream in the disc's own sectors, which nearly any player reads as an .mpg. Video CD carried films and karaoke across Asia through the 1990s and 2000s, pressed and pirated by the hundred million, with eight million players sold in China in 1997 alone, and a disc copied to a drive brings its .dat files along. Countless programs call their own files .dat, so a .dat is video only when it came from a disc.
A DVD stores its film as .vob files, Video Objects, from the DVD-Video standard of 1996: the disc's MPEG-2 video with its Dolby Digital sound, subtitle pictures and menus, in an MPEG program stream cut into files of a gigabyte because the disc's file system allowed no larger. They are what a DVD looks like copied straight onto a drive, in a VIDEO_TS folder beside the IFO files that hold the menus, and many were copied that way in the 2000s before ripping to a smaller file became the habit. The menus live in the IFO files, so a lone .vob plays without them.
Transport streams: TS, M2TS and MTS
MPEG-2 defined two ways to carry its video. The program stream, which DVD uses, assumes the file arrives intact. The transport stream assumes it does not, and is built for broadcast in 188-byte packets, so a receiver can pick up a signal mid-stream and survive a dropped packet. Digital television everywhere has been a transport stream since the standard of 1995, so a .ts file is a program recorded off the air or a satellite box, a piece of a live internet stream saved to disk, or the raw broadcast the anime scene shares before encoding, holding MPEG-2 or H.264.
Blu-ray and the AVCHD camcorders Sony and Panasonic introduced in 2006 use the same stream with a four-byte timecode on each packet, and call it .m2ts. A camcorder wrote it to its memory card as .mts, in a STREAM folder several levels down. Copied through the maker's software it became .m2ts; copied by hand it stayed .mts, so footage dragged straight off a card carries the shorter name. Inside is H.264 at full high definition, and the camcorder footage of the late 2000s and the copies of Blu-ray discs are in it.
DV
MiniDV was the digital camcorder tape Sony, Panasonic and the others agreed in 1995 and sold until about 2005, and its stream was lightly compressed video at the resolution of standard television, 25 megabits a second, which is 13 gigabytes an hour. A computer captured it over FireWire, usually into an .avi or a .mov but sometimes left bare as .dv. It is the home video of a decade, and a captured tape is one of these or its wrapped form.
Windows Media: ASF, WMV, WTV and DVR-MS
Microsoft built its streaming platform, NetShow, in 1996, and its container was named three times, the ActiveX Streaming Format at first, the Advanced Streaming Format within a year and the Advanced Systems Format in the end: the box built to stream over a modem and the one every Windows Media file is in. An .asf is usually an early Windows Media video from before the .wmv name arrived with Windows Media 7, or a stream someone saved.
Windows Media Video arrived in 1999, Microsoft's codec in the ASF container, for the years when Windows Media Player came with the operating system and a video on the web was a choice among it, RealPlayer and QuickTime. The clip sites of the early 2000s posted a video as a link to a .wmv and a right-click saved it, so a drive from those years holds them by the hundred. Windows Movie Maker, which came with Windows ME and XP, saved every home movie as one, so the camcorder tapes of the 2000s were digitized into it by the million, and the music and film stores of the time wrapped some in Windows Media DRM, which no longer unlocks. A Mac needed Microsoft's own Windows Media Player for Mac, which Microsoft stopped developing in January 2006 in favor of Telestream's free Flip4Mac plug-in for QuickTime.
Two more are Windows Media Center's. Windows XP Media Center Edition, from October 2002, made a PC with a tuner card and a remote into the living room's video recorder, and it recorded television as .dvr-ms, Microsoft Digital Video Recording, MPEG-2 in an ASF wrapper, often with copy protection. The TV Pack of 2008 replaced it with .wtv, Windows Recorded TV Show, a program off the air at several gigabytes an hour, often under the copy protection the broadcaster's flag asked for. Windows 10 dropped Media Center in 2015, and a protected recording has had no player since.
RealMedia: RM and RMVB
RealNetworks was Progressive Networks when it shipped RealAudio in 1995, and it added RealVideo in 1997, so RealMedia, .rm, is a container for both, built for a 28.8 modem: a clip was a small blurry window that paused to buffer. It was how the web watched anything before broadband, news clips, trailers and the first webcasts, through RealPlayer and its nagging upgrades.
RealMedia Variable Bitrate, .rmvb, is the 2000s form, with RealVideo 9 and 10 inside, which spent its bits where a scene needed them and so fit a film on one CD at better quality than DivX managed. It became the standard for the video traded across China, television episodes and films above all, and among anime fansub groups for most of that decade, and the RealPlayer on every Chinese PC played it.
Flash: SWF, FLV and F4V
FutureSplash Animator drew vector animations that played in a browser plug-in, and Macromedia bought the company in December 1996 and renamed the tool Flash. The Shockwave Flash file, .swf, is a program with drawings and sound in it, not a video: it held the shapes, the timeline, and the ActionScript that made a game a game, and it was the animation and game format of the web from the late 1990s until the 2010s, Newgrounds, Homestar Runner, the cartoons and games passed around by email, and the intro page of every corporate site of 2000. Adobe, which bought Macromedia in 2005, ended it: "Adobe stopped supporting Flash Player beginning December 31, 2020," and blocked Flash content from running the following month. Ruffle, "an open source Flash Player emulator" written in Rust, runs most of them in a browser now.
Flash Video, .flv, began with Flash Player 6 in 2002, which put Sorenson Spark video inside a Flash movie, and became a file of its own with Flash Player 7 in 2003: the file behind every video a Flash player drew on the web. YouTube served its videos as .flv from its first day in 2005 until it moved to MP4 around 2010, in Sorenson Spark at first and H.264 from 2008, so a video saved from YouTube or any other tube site in those years, through the savers that pulled the .flv out of the player, is one, usually at 320 by 240. In December 2007 Flash Player 9 Update 3 added H.264 and moved Flash's video to the MP4 container, and called the result .f4v: an MP4 under a Flash name, so a video saved from a Flash player of the late 2000s may be one, and renaming it .mp4 is all it ever needed.
Ogg video: OGV and OGM
The Xiph.Org Foundation makes free codecs and a free container, Ogg, to carry them, and Ogg has held video twice. Ogg Media, .ogm, was a 2002 stretch of the container to hold video, several audio tracks and subtitles at once, which nothing else on a PC did at the time, and it was the DVD-rip groups' format for a couple of years, a DivX or XviD picture with Vorbis sound and a subtitle track, until Matroska, built for that job, replaced it by 2004; Xiph discourages it now. Ogg Video, .ogv, is Xiph's own, most often holding Theora, the codec Xiph built from the VP3 that On2 donated in June 2002 and that Mozilla and Wikipedia backed in 2009 as the free codec the web's video tag should require. It lost that argument to H.264 and then to WebM, and Chrome removed Theora in version 123, in 2024, citing its declining use and "zero-day attacks against media codecs continuing to increase." Rare, and mostly a Wikipedia download or a free-software demo.
Matroska and WebM: MKV, MKA and WEBM
Matroska was announced on December 6, 2002 as a fork of the Multimedia Container Format, over whether to build the format on a binary form of XML, and the fork won. It is named for the Russian nesting doll, and open from the start: a container for any video and sound at all, with several audio tracks, soft subtitles and chapters in one file. The DVD-rip groups moved to it from OGM by 2004, the anime fansub groups followed later in the decade, when a release could carry the Japanese audio and a typeset subtitle track together, and it has been the file of the high-quality rip ever since. No video site sends one and Apple's players do not open it, but Windows has played it at the factory since the first Windows 10 preview in 2014, and MakeMKV, the common tool for copying a disc with every track intact, writes nothing else. Twenty-two years after the announcement the format became an internet standard, RFC 9559. .mka is the same container holding sound alone, a whole album in one file with chapters for its tracks, or a film's soundtrack in several languages pulled from a disc; it is far rarer than .mkv, since no ripper writes it by default.
WebM is Google's cut of Matroska for the web's video tag, announced at Google I/O on May 19, 2010 with the VP8 codec it had bought from On2 and opened. The project's own definition is short: "WebM is an open, royalty-free, media file format designed for the web," VP8, VP9 or AV1 video with Vorbis or Opus sound, with no patent fees on any of it. It is the video of the modern web's short clips, the animated GIF's replacement, and the file the imageboards, Reddit and Discord trade in, which is also why a clip saved from them often has no sound. Every browser plays it, Safari last, in April 2021 with macOS 11.3.
NSV
Nullsoft, the company behind Winamp, built internet television on the Shoutcast servers that streamed its radio, and Nullsoft Streaming Video was its format, VP3 or VP6 video with MP3 sound in a container as plain as the company could make it, with a Nullsoft Television service announced in 2003. A saved stream from that world is one, and the stations themselves were a few hundred hobbyists. Winamp played it and almost nothing else did.
Bink
RAD Game Tools' Bink Video, from March 1999, was the cutscene format of PC and console games for two decades, which a studio licensed because it decoded fast on a console with no spare processor and let the game ship on one disc. Its logo opened the game, and its .bik files sit in the folders of many installed games, Mass Effect among them. RAD's own player opened one outside a game, and FFmpeg 0.6, in June 2010, carried the reverse-engineered "Bink demuxer and audio/video decoders."
Sound
The PC had no sound to speak of until 1989, when Creative's Sound Blaster gave it a way to play recorded samples and a Yamaha chip to synthesize music, and the Amiga and the Mac had both from the start. The formats below divide by what they store: recorded sound as samples, which is large; music as instructions to a synthesizer, which is tiny; and, from 1993, recorded sound compressed by discarding what the ear cannot hear, the step that made music a file.
Sampled sound: WAV, AIFF, AU and VOC
The Waveform Audio File Format, .wav, came from the Multimedia PC specification of 1991 and Windows 3.1, Microsoft and IBM's way to store sound as the plain samples a CD does, in the same RIFF container as AVI. It is Windows' own sound: the chimes and dings of the Windows Media folder, the first step of every CD rip, the working file of every recording studio, and the sound effects of a decade of DOS and Windows games. A minute of CD-quality sound is ten megabytes, so it was never traded over a modem. Microsoft's documentation now files the whole interface under legacy, and the files play on.
Apple's Audio Interchange File Format, .aiff, is three years older, published in 1988 and built on Electronic Arts' IFF container from the Amiga: samples as recorded, with no compression. It is the file the Mac's own alert sounds ship as, what Mac music software wrote for twenty years, from Sound Designer to Logic, and what iTunes rips to when told to rip uncompressed, so music made or ripped on a Mac is full of it. .aif is the three-letter spelling, from the years a name had to fit DOS, and the spelling iTunes and the Music app still write when they rip to AIFF.
Sun's audio file, .au, came from its Unix workstations of the late 1980s and NeXT's, where the same file was .snd: usually 8-bit mu-law samples at 8 kilohertz, telephone quality, since the SPARCstation's audio chip was a telephone codec. It was the sound of the early web, the first thing Mosaic could play and the only sound Java's first applets could, so a 1990s web page's sound effect was one. Nothing writes it now, and other programs of the time used the .snd name for sounds of their own, so not every .snd is one.
Creative Voice, .voc, is the Sound Blaster's own file, from the card's launch in 1989, when a PC first had a way to play back a recording: 8-bit samples with the Sound Blaster's own blocks for silence and loops, recorded and played by the VOXKIT tool in the box. DOS games of the early 1990s shipped their speech and effects in it, so it dates from the start of PC multimedia beside the first .wav files, and Windows made WAV the standard by 1995.
MIDI: MID, MIDI and RMI
MIDI is a 1983 standard for connecting musical instruments, and a Standard MIDI File, which Dave Oppenheim wrote at Opcode and the MIDI Manufacturers Association adopted in 1988, holds what would have gone down the cable: no sound at all, only which key, when, how hard and on which instrument, so a song is a few kilobytes and sounds like whatever plays it, a Sound Blaster's FM chip in 1993 or a Roland Sound Canvas's samples. General MIDI, in 1991, fixed 128 instruments so a file made on one machine sounded roughly right on another. It was the music of DOS and Windows games through the mid-1990s, of Windows itself, which shipped canyon.mid with Windows 3.1, and of web pages that played a tune when they opened.
.mid is the DOS spelling and the common one, and .midi the four-letter one of the Mac, Unix and the software written after the three-letter limit was gone. .rmi is a MIDI file wrapped in Microsoft's RIFF container, the same wrapper WAV uses, from the Multimedia PC extensions of Windows 3.1 in 1992: Windows' own MIDI tools wrote it and Media Player plays it, and inside is an ordinary Standard MIDI File. Rare beside .mid, and Microsoft itself lists it as deprecated.
Trackers: MOD, 669, S3M, XM and IT
Karsten Obarski wrote The Ultimate Soundtracker for the Amiga in 1987 and invented a kind of music file: a set of recorded samples, plus patterns saying which sample plays at which pitch on which of the Amiga's four channels, tick by tick, down a screen laid out like a spreadsheet. A module sounded the same on every machine, since the samples traveled with it, and fit on a floppy. It was the music of the demo scene, of the BBS file areas, and of games on the Amiga and then the PC; the module, .mod, is its name, most files follow the ProTracker form that came after, and Modland and the Mod Archive hold them by the tens of thousands.
The PC caught up once it had a Sound Blaster or a Gravis Ultrasound to play samples on. Composer 669, from Tran of Renaissance in 1992, was among the first trackers written for the PC, with eight channels and a handful of effects, and the earliest PC demo and BBS music is in its .669 files and little after, since the scene moved on within two years; OpenMPT's list of module formats still reads them all. Scream Tracker 3, from Sami Tammilehto of Future Crew in 1994, the Finnish group whose demo Second Reality had defined the PC scene the year before, gave the PC what the Amiga had and more channels, with the Gravis Ultrasound to play them, and its .s3m carried the DOS demo scene and the BBS file areas of 1994 and 1995. FastTracker 2, from the Swedish demo group Triton in November 1994, added up to 32 channels and instruments with volume and panning envelopes rather than bare samples, and its extended module, .xm, is the format more tracker music of the middle and late 1990s is in than any other; Epic's Unreal and Deus Ex carried their music in it inside UMX packages. Impulse Tracker, from Jeffrey Lim in 1995, was the last and most capable of the DOS trackers, with 64 channels, stereo samples, filters and the note-off and volume-column effects the others lacked, and its .it carried the scene into the 2000s and is the format the tracker world still writes by preference. A collection of scene music runs from .mod through .s3m and .xm to .it.
MP3 and MP2
MPEG-1's audio standard of 1993 defined three layers of increasing complexity. Layer II, .mp2, became the sound of the Video CD, of DAB radio and of digital television, and a bare .mp2 is a track pulled from one of those or a broadcast recording. The Internet Underground Music Archive, which Rob Lord, Jeff Patterson and Jon Luini started at Santa Cruz in 1993, traded songs in it for two years before MP3 existed.
Layer III, from Karlheinz Brandenburg's group at Fraunhofer, was the one that changed things: a song at a tenth of a CD's size with most of what the ear hears. Fraunhofer released l3enc, the first software encoder anyone could run, on July 7, 1994, and the files it made were called .bit inside the institute until July 14, 1995, when the team voted on a name and, in Heise's account, settled on .mp3 "as the file extension for audio files compressed using their method." WinPlay3, the first player that decoded in real time on a PC, followed that September.
What followed is the history of music on computers. Winamp, 1997, played MP3s well on a Windows PC and was free; Napster, from June 1999, let 26 million people trade them at its peak in early 2001; the iPod, 2001, carried a thousand of them in a pocket; and the iTunes Store in 2003 was the record industry's answer, in a different format below. MP3 has been the common form of a music file since. Fraunhofer's licensing program ended on April 23, 2017, a week after the last United States patent expired, and the 128 kilobit files of the Napster years show their age in the swirl the encoders of the time left in a cymbal.
RealAudio: RA
Progressive Networks shipped RealAudio in April 1995, and it was the first sound that streamed over a modem: ABC News and National Public Radio at 14.4 kilobits a second, thin and muffled, but live, which nothing else on the internet was. That September 5 it carried the first Major League Baseball game streamed live over the internet, the Mariners at the Yankees, called by Dave Niehaus and Rick Rizzs for fans with "personal computers, internet connections, and newly developed audio software," who could "listen from virtually anywhere in the world." Seattle won 6 to 5. RealAudio was the internet's sound for the few years before MP3, through RealPlayer, and a clip saved from a 1990s radio site is one.
Windows Media Audio: WMA
Windows Media Audio was Microsoft's codec of 1999 and its answer to MP3, and the format Windows Media Player ripped a CD to at 128 kilobits unless told otherwise, through Windows XP and 7, so the CDs ripped on a Windows PC in the 2000s are in it whether or not anyone chose it. Some files carry the copy protection of the music stores of the time, Napster 2.0 and Microsoft's own among them, and those no longer play anywhere.
Ogg Vorbis: OGG
In September 1998 Fraunhofer sent a letter saying it would charge for MP3 encoders, and Christopher Montgomery's answer was Vorbis, in Xiph.Org's own Ogg container: in the foundation's words, "a fully open, non-proprietary, patent-and-royalty-free, general-purpose compressed audio format," and a better sound than MP3 at the same bitrate. Version 1.0 came out on July 19, 2002, with the shortest release note on this page, Montgomery's own: "Nothing much else to say. Vorbis 1.0 is officially out. Have at."
It never displaced MP3, because the iPod would not play it, but it became the sound of games, Minecraft among them, of every sound clip on Wikipedia, and of Spotify's streams for the service's first decade.
AAC: M4A, AAC and M4P
Advanced Audio Coding, the MPEG standard of 1997, was designed as the successor to MP3 and sounds better at the same bitrate, and it is the sound inside nearly every MP4 video, every iTunes song and every YouTube stream. Apple made it a consumer format on April 28, 2003, when the iTunes Music Store opened with 200,000 songs "for just 99 cents per song, without subscription fees," every one "encoded in the industry-standard AAC audio format at 128 kilobits per second." .m4a is AAC sound in an MP4 container under the name Apple gave it, and the rip format iTunes has used since; Voice Memos on every iPhone records to it, and Apple Lossless rides in the same container under the same name, so an iTunes library and a phone are largely made of them. A bare .aac is the stream without its container, in ADTS frames, which some rippers and radio recorders write.
.m4p is a protected purchase from those first years: an .m4a with Apple's FairPlay copy protection, AAC at 128 kilobits, playable only in iTunes on one of the three computers, five from 2004, authorized to the account that bought it. iTunes Plus offered the same songs unprotected from 2007, and on January 6, 2009 Apple announced that "all four major music labels" and thousands of independents were selling DRM-free, with an upgrade for the songs already bought "for just 30 cents per song." A purchase never upgraded stays locked.
Lossless: FLAC, APE and WV
Lossless compression packs a CD's sound to a little over half its size with every bit intact, and three formats competed for the collectors who wanted that. WavPack, .wv, came first, from David Bryant in August 1998, with a hybrid mode that splits a song into a small lossy .wv and a .wvc correction file that restores every bit; it never had FLAC's following, but a share of the lossless rips traded in the 2000s are in it, and it is the one lossless format that also packs DSD. Monkey's Audio, .ape, is Matthew Ashland's codec of 2000, a few percent smaller than FLAC and several times slower to decode; it was the format of the lossless trading circles of the 2000s before FLAC won, where a whole album was one .ape with a .cue beside it saying where the tracks begin.
The Free Lossless Audio Codec, .flac, is Josh Coalson's, begun in 2000 and released in July 2001, under Xiph.Org since 2003, and it checks each frame against a hash. It is the format of the exact CD rip made with Exact Audio Copy, of the Bandcamp download, of the concert recording traded among fans since the days of Shorten, and of the lossless collection as such. Apple held out against it until 2017, the last to.
Opus
Opus was standardized by the IETF in September 2012 as RFC 6716, from Xiph.Org's CELT and Skype's SILK, and its abstract says what it is for:
This document defines the Opus interactive speech and audio codec. Opus is designed to handle a wide range of interactive audio applications, including Voice over IP, videoconferencing, in-game chat, and even live, distributed music performances. It scales from low bitrate narrowband speech at 6 kbit/s to very high quality stereo music at 510 kbit/s.
It is the codec of speech and music online now: every WhatsApp voice note since 2016, every Discord call, and the sound under YouTube's video in a WebM. It usually travels inside an .ogg or a .webm; a file named .opus is Ogg, and a collector who pulls sound off YouTube gets them by the hundred.
Surround: AC3 and DTS
Dolby Digital, Dolby's AC-3, was in cinemas from Batman Returns in 1992 and on DVD from the format's launch, where it is the surround sound every player must decode: five channels and a subwoofer in 384 or 448 kilobits. A bare .ac3 is a soundtrack pulled from a disc in the 2000s, kept beside the .vob or the rip for a home theater's receiver to decode. Digital Theater Systems' format opened with Jurassic Park in 1993, Steven Spielberg being among the company's first investors, and became the alternative to Dolby on DVD and Blu-ray at 768 kilobits or 1.5 megabits, up to three times Dolby's. A bare .dts is a disc's soundtrack extracted, and a few hundred albums were released as DTS Music Discs, ordinary CDs that a receiver decoded into surround.
AMR
Adaptive Multi-Rate is the speech codec 3GPP adopted as the standard for its phones in 1999, and the file a Nokia or a Sony Ericsson of the 2000s saved a voice memo or a recorded call as, in frames of 4.75 to 12.2 kilobits. It holds speech and little else, at telephone quality, so a minute is under a hundred kilobytes, small enough for the networks of the time, and Android phones can still record it.
Beside the media
A collection holds files that are not media but say what to do with it: lists of what to play in what order, a map of where the tracks are in a disc image, and the words of a film in a language its soundtrack is not. They are small text files, and a folder of music or video rarely lacks one.
Playlists: M3U, M3U8, PLS and XSPF
The M3U playlist began with Fraunhofer's WinPlay3 and became the playlist of Winamp in 1997: a text file listing the paths of songs, one per line, in the order to play them, with a comment line per track for its title and length. Every music player since has read it, internet radio stations hand one out to start a stream, and playlists from the MP3 years are in it, pointing at files that have since moved. .m3u8 is the same file written in UTF-8, so a song with an accent in its name is found; the 8 names the encoding. Music players began writing it in the 2000s, and Apple took it in 2009 as the index of an HTTP Live Stream, a list of ten-second segments, which RFC 8216 later wrote down, so a .m3u8 today may be a playlist of songs or the recipe of a stream, and the second kind is far more common.
The PLS playlist came from codeArts' museArc player and was adopted by Shoutcast, Nullsoft's internet radio of 1998: a small text file in Windows' INI style, a numbered File1, Title1 and Length1 per entry, naming a station's stream or a set of songs. Clicking one on a radio site opened it in Winamp, and one saved from those years names a stream that may no longer exist; Shoutcast's directory still hands them out. XSPF, pronounced spiff, is Xiph.Org's open playlist, declared final in January 2005, which could name a song by its title, artist and album rather than a path alone; VLC adopted it as its own, and a playlist saved from VLC is one.
Cue sheets: CUE
A cue sheet came from Golden Hawk Technology's CDRWIN, the CD burning program of the mid-1990s: a text file saying where each track starts, to the frame, in a single file holding a whole disc, and what the disc and its tracks were called. It is how a CD ripped as one .ape, .flac or .wav still knows its tracks and how one is burned back exactly, so it sits beside those files in every lossless collection, and Exact Audio Copy writes one with each rip.
Subtitles: SRT
SubRip, from March 2000, read a DVD's subtitle pictures with optical character recognition and wrote them out as text: a number, a start and end time to the millisecond, and the lines, for each subtitle. Its file, .srt, became the one subtitle format everything reads, and a downloaded film or series comes with one beside it, named to match.
What is not here
Some formats were everywhere for a few years and are named on no list of what a program opens, because nothing opens them and nothing will. AOL rewrote every picture its twenty million subscribers saw into its own .art format, and only AOL's software read it. Liquid Audio sold music with copy protection from 1997 until it closed in 2002. Sony's OpenMG wrapped every song moved to a MiniDisc or an early Walkman in encryption that only SonicStage understood. Audible's audiobooks, since 1997, are locked to the account that bought them. Macromedia Director's Shockwave movies were the CD-ROM era's interactive multimedia and the web's games before Flash, and run now only in an emulator.
They belong in this history and not in a list of file types a program might one day open, because their keys, their players or their companies are gone. A collector who has them has them as a record of a time, which is a fine reason to keep them.
Sources
The links above are the specifications and announcements where those are public, and Wikipedia where the history is best told in one place. Three more cover anything this page does not. The Encyclopedia of Graphics File Formats, from 1996, is the reference for the picture formats of that era, and its summaries are online. Just Solve the File Format Problem, Archive Team's wiki, is the fullest catalog of everything else, including the orphans. And the Library of Congress's format descriptions say, for each format, what an archive needs to know to keep it readable, which is the question this page is about.