These extensions at the end of a filename refer to the type of file it is. This information is used by your operating system to launch an appropriate program when you click on the filename. Example: file.txt is a text file and can be opened by a text editor program.

.$$$Temporary file
.2GRA file that allows Windows to display text and graphics in standard mode on a 286 or 386 computer (filename extension).
.386Swap file; enables computer running in enhanced mode to use Windows with virtual memory (filename extension).
.3GRA file that allows Windows to display text and graphics in enhanced mode on a 386, 486, or Pentium computer (filename extension).
.906Calcomp plotter
.A3WMacroMedia Authorware Windows 3.5 (filename extension).
.ABKAutoBackup, Corel Draw (filename extension).
.ABRBrush - Adobe Photoshop (filename extension).
.ACLKeyboard accelerator, Corel Draw 6 (filename extension).
.ACMWindows system directory file (filename extension).
.ACVDrivers for compressing or decompressing audio files, OS/2 (filename extension).
.ADAfter Dark
.ADB1. Appointment DataBase, HP 100LX (filename extension). 2. Body file type, Ada language (filename extension).
.ADDAdapter Driver - OS/2 (filename extension).
.ADMAfterDark MultiModule (filename extension).
.ADRAfterDark Randomizer (filename extension). AfterDark is a screensaver program that can be set to randomly display a variety of screensaver patterns one after another.
.ADSSpecification file type, Ada language (filename extension).
.AFMAdobe Font Metrics - Type 1 font metrics (filename extension).
.AG4Access G4
.AIAdobe Illustrator
.AIFAudio Interchange File Format or AIFF (filename extension). A format developed by Apple Computer for storing high-quality sampled audio and musical instrument information. It can be played on PC and Mac.
.aiffAudio Interchange File Format. An uncompressed sound format developed by Apple Computer for storing high-quality sampled audio and musical instrument information. It can be played on PC and Mac, using QuickTime or Sound Player.
.ALLArts and Letters Library (filename extension).
.ANIAnimated cursor (filename extension).
.ANSANSI text (filename extension).
.APIApplication Program Interface (filename extension). An interface between the operating system and application programs.
.APPMacroMedia Authorware package (filename extension).
.ARCARC or ARC+ compressed
.arjA PC compressed format found on European sites (filename extension), which can be decoded with unArjMac, DeArj, and SITEX10.EXE (win).
.ARTAn art file, in some draw or paint applications (filename extension).
.ASCASCII text file
.ASFActive Streaming File - HoTMetaL Pro (filename extension).
.ASMAssembly Source Code
.ASPActive Server Page - Microsoft (filename extension).
.ASTAssistant file - Claris Works (filename extension). Assistants guide the user through a task by asking a series of questions and then use the answers to perform a task. Assistants in Claris Works can be used to create such useful items as calendars, newsletters, stationery, labels, and address lists, to make footnotes within a file, to find documents, etc.
.AUA sound file format used on Sun Microsystems or other UNIX computers
.AVIAVI movie format
.AVSIntel video capture format (filename extension).
.b64Base 64 (filename extension), the encoding format used by the Multipurpose Internet Mail Extension.
.BAKBackup copy in DOS or OS/2
.BASBASIC program file
.BFCBriefcase document - Windows 95 (filename extension).
.BGBackgammon game (filename extension).
.BIBinary file (filename extension).
.binA MacBinary II encoded file (filename extension). This file type, downloaded as MacBinary or Binary, can be decompressed with Stuffit Expander..
.BKBackup copy
.BK$Backup file (filename extension).
.BLTWordperfect for DOS (filename extension).
.BNKSim City game file (filename extension).
.BRXBrowse Index (filename extension). Found on multimedia CD-ROMs.
.BTMBatch file - Norton Utilities (filename extension).
.CC program file
.CABMicrosoft compressed format
.CALCalendar or CALS
.CBTComputer-Based Training; a tutorial file (filename extension).
.CCHCorel chart (filename extension).
.CCMLotus cc:Mail (filename extension).
.CDACD Audio track (filename extension).
.CDTCorel Draw template (filename extension).
.CDXCorel Draw compressed file (file extension).
.CDXVisual FoxPro database index (filename extension).
.CFBCompton’s multimedia encyclopedia (filename extension).
.CFLCorel Flow (filename extension).
.CGICommon Gateway Interface (filename extension). A file that makes it possible for HTTP servers to interface with computer programs to provide interactive functions like fill-out forms.
.CGMCGM graphics
.CHKCheckdisk - DOS
.CHPChapter - Ventura
.CIFChapter Information - Venture
.CIMSim City file (filename extension).
.CITIntergraph scanned image
.CMDCommand file -- OS/2
.CMFCorel MetaFile (filename extension).
.CMFSoundBlaster file (filename extension).
.CMPLEAD Technologies graphics
.CMVCorel Move animation (filename extension).
.CNFConfiguration file (filename extension).
.CNQCompuworks Design Shop (filename extension).
.COBCOBOL source code
.COMCommand file - small version of .EXE
.CPEFax Cover document (filename extension).
.CPICode Page - DOS
.CPLControl Panel - Windows
.CPPC++ program file
.CPRKnowledge Access graphics
.CPTCompact Pro
.CPXCorel Presentation Exchange compressed file (filename extension).
.CRDWindows Cardfile (filename extension).
.CSCCorel Script (filename extension).
.CSSCascading Style Sheet (filename extension).
.CSVComma delimited
.CTLControl file (filename extension).
.CTYCity file - SimCity (filename extension).
.CURWindows cursor image
.CUTDr. Halo graphics
.CVMicrosoft CodeView (filename extension).
.CWKClaris Works (filename extension).
.CWSClaris Works template (filename extension).
.DBTable - Paradox
.DBCVisual FoxPro database (filename extension).
.DBFDatabase File - dBASE
.DBTDatabase text - dBASE
.DCAIBM text
.DCSColor Separation - EPS
.DDDisk Doubler
.DDIDisk Doubler Image (filename extension).
.DEFDefinition - C++ (filename extension).
.DERCertificate (filename extension).
.DEVDevice driver file (filename extension).
.DGAutotrol graphics
.DGNIntergraph graphics
.DIBDIB graphics - Windows
.DIFData Interchange Format spreadsheet
.DLLDynamic link library
.DOCDocument file
.DOTDocument Template - Microsoft Word (filename extension).
.DOXMultiMate document
.DPIDots Per Inch - graphics
.DPRDelphi project file (filename extension).
.DRWDesigner graphics
.DS4Designer graphics, version 4
.DSFDesigner graphics, version 6
.DWGAutoCAD vector format
.DWGDrawing - AutoCAD (filename extension).
.DXDocument Imaging
.DXFAutoCAD vector format
.ED5EDMICS graphics
.EMFEnhanced Windows Metafile (filename extension).
.emlelectronic mail
.EPSEncapsulated PostScript format
.ESIEsri plot file
.EXEExecutable file -- machine code
.FDXForce Index
.FH3Aldus Freehand 3 (filename extension).
.FLCAutoDesk animation
.FLDThumbnail folder - Hijaak
.FLIAutoDesk animation
.FLRLive3D (filename extension).
.FLTFilter - graphics conversion
.FMFramemaker (filename extension).
.FM3Format for 1-2-3 Version 3
.FMTFormat - dBASE
.FOGFontographer font (filename extension).
.FON1. Bitmapped Font - Windows 2. Phone
.FOTWindows TrueType font
.FPClaris FileMaker Pro (filename extension).
.FP1Flying Pigs (filename extension).
.FP3Filemaker Pro 3
.FPXFlashPix bitmap (filename extension).
.FRMForm design -- Visual Basic
.FRSWordPerfect Graphics Driver
.G4GTX RasterCAD
.GCAGOCA graphics
.GEDArts & Letters graphics
.GEMGEM graphics
.GEOVideoScope (filename extension).
.GIFGraphics Interchange Format
.GP3CCITT compressed Group 3 TIFF file (filename extension).
.GP4Group 4 - CALS, ITU (filename extension). CCITT compressed Group 4 TIFF file.
.GRAMicrosoft Graph (filename extension).
.GX1Show Partner graphics
.GX2Show Partner graphics
.GZGNU gzip compressed file - Unix
.HHeader (filename extension -- C).
.HDFHierarchical Data File
.HEDHighEdit document (filename extension).
.HELMicrosoft Hellbender game file (filename extension).
.HGLHP Graphics Language (filename extension).
.HPJHelp Project - Visual Basic (filename extension).
.HPLHP Graphics
.HQXBinHex (filename extension -- Macintosh).
.HTHyperTerminal (filename extension).
.htmDOS filename extension for a document with HTML coding, which can be read by WWW browsers.
.htmlFilename extension for a document with HTML coding, which can be read by WWW browsers.
.HWPHangul Word Processor (filename extension).
.HYCHyphenation - WordPerfect
.ICAIOCA graphics
.ICBTarga bitmap (filename extension).
.ICMImage Colour Matching (filename extension).
.ICOIcon - Windows or OS/2
.ICONSun icon and cursor
.IDDInstrument Definition - MIDI (filename extension).
.IDEIntegrated Development Environment configuration (filename extension)
.IGFInset Systems graphics - Hijaak
.IIFInterchange File - QuickBooks for Windows (filename extension).
.ILIcon Library
.imaWinimage compressed format These files can be decoded or mounted by ShrinkWrap.
.imageMac disk image (filename extension); a compressed format which can be decoded or mounted by DiskCopy, Disk Image Mounter, Disk Charmer, and ShrinkWrap (ImageMaster).
.IMGImage. This file is a Macintosh Disk Image. Disk Copy can be used to mount the disk image on the Macintosh desktop. The mounted disk image will behave like a read-only disk.
.INIInitialization - configuration settings
.IOBImagine file (filename extension).
.ISUNetscape file (filename extension).
.ITMOD music file format (filename extension).
.IWIdlewild screensaver (filename extension).
.IXIndex File - Framemaker (filename extension).
.JFF or .JFIFJPEG File Interchange Format; a 24-bit graphic format. It can be opened with QuickTime, a WWW browser, or a graphics viewer such as JPEGView.
.JIFJPEG Image Format (filename extension).
.JPEGJPEG bitmap (filename extension).
.JPGfile extension for JPEG (Joint Photographic Experts Group). A file stored in JPEG format. JPEG,an ISO/ITU standard for storing images with high compression capability, uses a discreet cosine transform that can achieve compression rates of 100:1 (significant loss of data from original) and 20:1 (minimal loss). C-Cube Microsystems introduced the first JPEG chip.
.JTFJPEG bitmap (filename extension).
.KDCKodak Photo-Enhancer (filename extension).
.LBLLabel - dBASE
.LBMDeluxe Paint graphics file
.LDBLock file - Microsoft Access (filename extension).
.LEGLegacy document (filename extension).
.lhaFilename extension for a PC/Amiga compression format decodable by LHA Expander or MacLHA.
.lhsLiterate Haskell source file
.lhzLHA compression file
.LICLicense file - shareware (filename extension).
.LSTList (filename extension).
.LWPLotus Word Pro document (filename extension).
.LZHLHARC compression
.lzsPC/Amiga compression format
.M3DMotion 3D - Corel (filename extension).
.MAFMicrosoft Access Form (filename extension).
.MAMMicrosoft Access Macro (filename extension).
.MAPMap - linkage editor
.MAQMicrosoft Access Query (filename extension).
.MARMicrosoft Access Report (filename extension).
.MATMicrosoft Access Table (filename extension).
.MCSMathCAD format
.MCWMicrosoft Word for Macintosh (filename extension).
.MDBAccess database
.METMetafile - OS/2
.MFFMIDI File Format (filename extension).
.MGFMicrografx Draw Font (filename extension).
.MIMiscellaneous (filename extension).
.MICMicrosoft Image Composer (filename extension).
.MIFFAn ImageMagick file format
.MILGroup 4
.mimeMIME (filename extension); the encoding format used by the Multipurpose Internet Mail Extension.
.MMEMime encoded file (filename extension); the encoding format used by the Multipurpose Internet Mail Extension.
.MMFMicrosoft Mail File (filename extension).
.MMMMacromind animation
.MOD(For module). A music file format that contains digitized sound samples A .MOD file takes more memory than a MIDI file because a MIDI file contains instructions for making sounds but not the actual sound samples. There are .MOD players for Amiga, PC, and Macintosh computers.
.moovQuickTime movie. This file can be viewed with QuickTime Player.
.MOVMovie - QuickTime
.movieQuickTime movie. This file can be viewed with QuickTime Player.
.MOZMozilla - Netscape cache file (filename extension).
.mp2MPEG Layer II compressed audio. This file can be played using QuickTime Player and some other sound players.
.mp3MPEG Layer III compressed audio. This file can be played with QuickTime Player, Real Player, and some other sound players.
.MPEMPEG (filename extension).
.MPEGMPEG movie or animation file. This file can be played with QuickTime Player.
.MPGMPEG encoded file. This file is an MPEG movie, and can be played with QuickTime Player.
.MPNTMacintosh MacPaint
.MPPMicrosoft Project project file (filename extension).
.MPTMicrosoft Project template file (filename extension).
.MPXMicrosoft Project export file (filename extension).
.MRKMarkup - Informative Graphics
.MSGMessage file
.MSNMicrosoft Network document (filename extension).
.MSPMicrosoft Paint
.MUSMusic (filename extension).
.MVBMicrosoft Multimedia Viewer (filename extension).
.MYSMyst saved game file (filename extension).
.NDXIndex - dBASE
.NETNetwork file (filename extension).
.NGNorton Guides
.NLMNLM program - NetWare
.NTFNotes Template File - Lotus Notes database (filename extension).
.OABOutlook Address Book - Microsoft (filename extension).
.OBDMicrosoft Office Binder (filename extension).
.OBJObject module
.OCXObject Linking and Embedding (OLE) Custom Control (filename extension).
.OLBOLE Object Library (filename extension).
.OLEOLE object (filename extension).
.ONXOnyx Graphics Postershop (filename extension).
.OVLOverlay module
.OVROverlay module
.OZMSharp Organizer memo bank
.OZPSharp Organizer telephone bank
.P10Tektronix Plot10
.PABPersonal Address Book - Microsoft (filename extension).
.PAKQuake game data (filename extension).
.PALPaintbrush palette (filename extension).
.PASPascal program file
.PATPattern - Corel Draw (filename extension).
.PBKMicrosoft Phonebook (filename extension).
.PBMPortable Bit Map
.PCDPhoto CD format
.PCLHP LaserJet
.PCMLaserJet cartridge information
.PCSPICS animation (filename extension).
.PCTPC Paint
.PCWPC Write
.PCX1. PC Paintbrush 2. Graphics file - Zsoft format
.PDGPrintShop Deluxe (filename extension).
.PDVPC Paintbrush printer driver
.PFAType 1 font - ASCII
.PFBType 1 font - encrypted
.PFMPostscript Font Metrics; Windows Type 1 font metrics
.PGLHPGL 7475A plotter - vector graphics
.PGMPortable Gray Map bitmap (filename extension).
.PHTMLHTML document with preprocessing instructions (PPIs) (filename extension).
.PICPICT graphics format, or PIXAR picture file
.PICTMacintosh QuickDraw/PICT This kind of file stores images in QuickDraw vector format. PICT2 can have grayscale bitmapped images also.
.PIFProgram Information File - Windows
.PITPackIt - Macintosh compression
.PIXInset Systems graphics
.PJXProject file - Visual FoxPro (filename extension).
.pkgAppleLink package compression format These files are decodable by StuffIt Expander.
.PLPerl script (filename extension).
.PLTPlotter drawing (filename extension).
.PM3PageMaker 3 document
.PM4PageMaker 4 document
.PM5PageMaker 5 document
.PNG1. Portable Network Graphics bitmap (filename extension). 2. Paint Shop Pro Browser (filename extension).
.POVPersistence Of Vision raytracer (filename extension).
.PPAPowerPoint Add-in - Microsoft (filename extension).
.PPDPostScript Printer Description
.PPMPortable PixelMap (filename extension).
.PPSPowerPoint Slideshow (filename extension).
.PPTPowerPoint presentation (filename extension).
.PRDPrinter driver - Microsoft Word, Word Perfect, Microsoft Works (filename extension).
.PRGA dBASE source code file
.PRJProject file
.PRN1. Print file - temporary 2. XyWrite printer driver 3. PostScript file
.PRSWordPerfect printer driver
.PRTFormatted text
.PSPostScript. This is a plain text file.
.PSDPhotoshop Document
.PUBPublication - Ventura Publisher, Microsoft Publisher (filename extension).
.PWDPocket Word document - Microsoft (filename extension).
.PWZMicrosoft PowerPoint Wizard (filename extension).
.PXLMicrosoft Pocket Excel (filename extension).
.QBWQuickBooks for Windows (filename extension).
.QDKQuarterdeck Qemm (filename extension).
.QLBQuick Library (filename extension).
.QLCATM font information
.QRYMicrosoft Query (filename extension).
.qtQuickTime movie, binary file type (filename extension). .
.QTMQuickTime Movie (filename extension).
.R8LLaserJet landscape font
.R8PLaserJet portrait font
.RAMReal Audio
.RASRaster graphics - Sun
.RAWRaw file format - bitmap (filename extension).
.rcA filename extension found in many UNIX files (.newsrc, etc.) which means "run commands".
.RECWindows Recorder macro file (filename extension).
.REGRegistration file (filename extension).
.REPReport file (filename extension).
.RFTRFT-DCA (filename extension).
.RGBAn SGI RGB image file
.RIAAlpharel Group IV raster graphics
.RIBRenderman graphics
.RICRoch FaxNet
.RIFFractal Painter bitmap (filename extension).
.RIFFResource Interchange File Format A multimedia file format; the Microsoft equivalent to Amiga IFF format.
.RIXRIX virtual screen
.RLAWavefront raster image
.RLCCAD Overlay ESP - Image Systems
.RLERun Length Encoded
.RMReal Media.
.RNDAutoShade format
.RNLGTX Runlength raster graphics
.RPTReport file (filename extension).
.RTFMicrosoft text and graphics
.SAssembly language file - Unix
.S3MMOD music file (filename extension).
.SAVSaved game (filename extension).
.SBPIBM Storyboard graphics / Superbase text
.SCSource Code - Paradox
.SCMScreenCam movie
.SCPDial-up networking script (filename extension).
.SCR1. Screensaver - Windows. 2. Screen Layout - dBASE. 3. Script for Apple's Disk Copy utility.
.SCTScreen Capture Text - Lotus
.SDLSmartDraw Library (filename extension).
.SEASelf-Extracting Archive (Stuffit or Compact Pro)
.SEGSegment (of a compressed file saved in segments with Stuffit or Compact Pro)
.SEPTIFF bitmap (filename extension).
.SETSetup parameters
.SFLLaserJet landscape font
.SFPLaserJet portrait font
.SFSPCL 5 scalable font
.sharUNIX shell archive (filename extension), which can be decoded by Unshar.
.SHTMLHTML file with embedded server-side includes (SSIs) (filename extension).
.SISoftImage image file
.sigSignature A .sig file can be set up and automatically attached to outgoing email, newsgroup postings, etc. It includes the name and contact information of the sender, and may also have ASCII art, favorite quotes, etc.
.SITStuffit compressed file
.SLDAutoCAD slide
.SLKSymbolic Link (SYLK) spreadsheet (filename extension).
.SMISelf-Mounting Image. This file is a Macintosh Disk Image, similar to an .img file, but it does not require the use of Disk Copy. When the file is downloaded, a disk image appears on the desktop. The disk image will behave like a read-only disk.
.SNDSound file
.SNMNetscape mail (filename extension).
.SPDSpeedo scalable font
.spxScreen Peace Extension
.SQBSyQuest Backup (filename extension).
.SRCA file used in the creation of .INI files for configuration settings (filename extension).
.STYStyle sheet - Ventura
.SVXAmiga 8SVX sound (filename extension).
.SWPSwap - temporary file (filename extension).
.SYDSysedit backup file (filename extension).
.SYLSYLK spreadsheet format
.SYNUSDSC Synu image
.SYSSystem file
.TALAdobe Type Align
.TARTar - Tape ARchive (filename extension). Tar is a UNIX method of archiving files, which can also be used by PCs. Tar archives files but does not compress them, so sometimes .tar files are compressed with other utilities, which produces extensions like .tar.gz, .tar.Z, and .tgz. Archive files with the .tar extension can be extracted in UNIX with tar or on a PC with WinZip or on the Mac with the program Tar.
.tar.gzCombined filename extension for a file that has been archived using tar and then gzipped.
.tar.z or .tar.ZCombined filename extension for a file that has been archived using tar and then zipped.
.tazAnother way of writing .tar.Z
.TBKAsymetrix Toolbook (filename extension).
.TDFTypeface definition - Speedo
.TEXTex or LaTex document
.TFMFont metrics - Intellifont
.TGATARGA graphics
.tgzAnother name for .tar.z and .tar.gz
.THEMEDesktop theme - Windows 95 (filename extension).
.THNThumbnail (filename extension).
.TIFTIFF graphics file
.TIFFTIFF graphics file (filename extension).
.TLBOLE Type Library (filename extension).
.TMPTemporary file
.TOCTable Of Contents (filename extension).
.TRMTerminal settings - Windows (filename extension).
.TTCTrueType compressed font
.TTFTrueType font
.TWFTabWorks File (file extension).
.TX8MS-DOS text (filename extension).
.TXTASCII text file
.USLLaserJet landscape font
.USPLaserJet portrait font
.uuUuencode compressed file
.uueUuencode file
.VBPVisual Basic Project (filename extension).
.VBXVisual Basic Extension
.VDATarga bitmap (filename extension).
.VIFFKhoros Visualization image file
.VLBVentura Library (filename extension).
.VOCSound Blaster
.VPVentura Publisher (filename extension).
.VSTTarga bitmap (filename extension).
.VUERelational View - dBASE
.VXDVirtual Device Driver (filename extension).
.WABWindows Address Book (filename extension).
.WAVSound file
.WBKMicrosoft Word Backup (filename extension).
.WDBMicrosoft Works Database (filename extension).
.WIDVentura width table (filename extension).
.WINWindows backup file (filename extension).
.WIZMicrosoft Word Wizard (filename extension).
.WK1Lotus 1-2-3, up to 2.01
.WK3Lotus version 3
.WK4Lotus version 4
.WKQQuattro spreadsheet
.WKS1. Lotus Worksheet (filename extension). 2. Microsoft Works document (filename extension).
.WMFWindows Metafile
.WPD1. Windows Printer Description (filename extension). 2. WordPerfect Demo (filename extension). 3. WordPerfect Document (filename extension).
.WPGWordPerfect Graphics
.WPMWordPerfect macro
.WPSMicrosoft Works document
.WPTWordPerfect Template (filename extension).
.WRIWindows Write document
.WRKSymphony spreadsheet
.WS1WordStar for Windows 1 document (filename extension).
.WS2WordStar for Windows 2 document (filename extension).
.WS3WordStar for Windows 3 document (filename extension).
.WS4WordStar for Windows 4 document (filename extension).
.WS5WordStar for Windows 5 document (filename extension).
.WS6WordStar for Windows 6 document (filename extension).
.WS7WordStar for Windows 7 document (filename extension).
.WVLWavelet compressed bitmap (filename extension).
.XAVS X image file
.XARCorel Xara drawing (filename extension).
.XBMX Bitmap
.XIFXerox Image Format (filename extension).
.XLCExcel chart
.XLKMicrosoft Excel backup (filename extension).
.XLMMicrosoft Excel macro (filename extension).
.XLSExcel worksheet
.XLTMicrosoft Excel template (filename extension).
.XMMOD music format (filename extension).
.XPMX Pixelmap
.XWDX Window System window dump image
.XXEXxencoded file (filename extension).
.YALArts & Letters click art (filename extension).
.ZUnix compress file
.ZIPFile compressed using PKZIP
assistantsA special kind of file used by Claris Works. Assistants guide the user through a task by asking a series of questions and then use the answers to perform a task. Assistants in Claris Works can be used to create such useful items as calendars, newsletters, stationery, labels, and address lists, to make footnotes within a file, to find documents, etc.
bad fixA failed attempt to repair a computer bug; a fix that doesn't work or that introduces new and unexpected problems. The expression has cropped up a lot in relation to Y2K fixes.
LHAA DOS compression program. Compressed files have the extension .lhz.
MBXMessage Base - Eudora (filename extension).

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