.A3W  MacroMedia Authorware Windows 3.5 
.ABK  AutoBackup, Corel Draw 
.ABR  Brush - Adobe Photoshop 
.ACL  Keyboard accelerator, Corel Draw 6 
.ACM  Windows system directory file 
.ACV  Drivers for compressing or decompressing audio files, OS/2 
.AD  After Dark
.ADB Appointment DataBase, HP 100LX; Body file type, Ada language 
.ADD Adapter Driver - OS/2 
.ADM AfterDark MultiModule 
.ADR AfterDark Randomizer 
.ADS Specification file type, Ada language 
.AFM Adobe Font Metrics - Type 1 font metrics 
.AG4 Access G4
.AI Adobe Illustrator
.AIF Audio Interchange File Format or AIFF 
.ALL Arts and Letters Library 
.ANI Animated cursor 
.ANS ANSI text 
.API Application Program Interface 
.APP MacroMedia Authorware package 
.ARC ARC or ARC+ compressed
.arj A PC compressed format found on European sites
.EXE (win)
.ART An art file, in some draw or paint applications 
.ASC ASCII text file
.ASF Active Streaming File - HoTMetaL Pro 
.ASM Assembly Source Code
.ASP Active Server Page - Microsoft 
.AST Assistant file - Claris Works 
.ATT AT&T
.AU A sound file format used on Sun Microsystems or other UNIX computers
.AVI AVI movie format
.AVS Intel video capture format 
.b64 Base 64, MIME encoding
.BAK Backup copy in DOS or OS/2
.BAS BASIC program file
.BAT Batch
.BFC Briefcase document - Windows 95 
.BG Backgammon game 
.BI Binary file 
.BIN Driver
.bin A MacBinary II encoded file 
.BK Backup copy
.BK$ Backup file 
.BLT Wordperfect for DOS 
.BMP Bitmap
.BNK Sim City game file 
.BRX Browse Index 
.BTM Batch file - Norton Utilities 
.C C program file
.CAB Microsoft compressed format
.CAL Calendar or CALS
.CAP Caption
.CBT Computer-Based Training; a tutorial file 
.CCH Corel chart 
.CCM Lotus cc:Mail 
.CDA CD Audio track 
.CDR CorelDraw
.CDT Corel Draw template 
.CDX Corel Draw compressed file (file extension)
.CDX Visual FoxPro database index 
.CFB Comptons multimedia encyclopedia 
.CFG Configuration
.CFL Corel Flow 
.CGI Common Gateway Interface 
.CGM CGM graphics
.CHK Checkdisk - DOS
.CHP Chapter - Ventura
.CIF Chapter Information - Venture
.CIM Sim City file 
.CIT Intergraph scanned imoaID
.ED5  EDMICS graphics
.EMF  Enhanced Windows Metafile 
.eml  electronic mail
.enc  encoded
.EPS  Encapsulated PostScript format
.ESI  Esri plot file
.EXE  Executable file -- machine code
.FAX  Fax
.FDX  Force Index
.FH3  Aldus Freehand 3 
.FLC  AutoDesk animation
.FLD  Thumbnail folder - Hijaak
.FLI  AutoDesk animation
.FLR  Live3D 
.FLT  Filter - graphics conversion
.FM  Framemaker 
.FM3  Format for 1-2-3 Version 3
.FMT  Format - dBASE
.FNT  Font
.FOG  Fontographer font 
.FON  Bitmapped Font - Windows ; Phone
.FOR FORTRAN
.FOT Windows TrueType font
.FOX FoxBase
.FP Claris FileMaker Pro 
.FP1 Flying Pigs 
.FP3 Filemaker Pro 3
.FPX FlashPix bitmap 
.FRM Form design -- Visual Basic
.FRS WordPerfect Graphics Driver
.G4 GTX RasterCAD
.GCA GOCA graphics
.GED Arts & Letters graphics
.GEM GEM graphics
.GEO VideoScope 
.GIF Compuserve's Graphics Interchange Format
.GLY Glossary
.GP3 CCITT compressed Group 3 TIFF file 
.GP4 Group 4 - CALS, ITU; CCITT compressed Group 4 TIFF file
.GRA Microsoft Graph 
.GRF Graph
.GRP Group
.GX1 Show Partner graphics
.GX2 Show Partner graphics
.GZ GNU gzip compressed file - Unix
.H Header (filename extension -- C)
.HDF Hierarchical Data File
.HED HighEdit document 
.HEL Microsoft Hellbender game file 
.HGL HP Graphics Language 
.HLP Help
.HPJ Help Project - Visual Basic 
.HPL HP Graphics
.HQX BinHex (filename extension -- Macintosh)
.HST Host
.HT HyperTerminal 
.htm DOS HTML extension
.html HTML
.HWP Hangul Word Processor 
.HYC Hyphenation - WordPerfect
.HYP Hyphenation
.ICA  IOCA graphics
.ICB  Targa bitmap 
.ICM  Image Colour Matching 
.ICO  Icon - Windows or OS/2
.ICON  Sun icon and cursor
.IDD  Instrument Definition - MIDI 
.IDE  Integrated Development Environment configuration 
.IDX  Index, normally associated with database files
.IFF  Amiga multimedia file type
.IGF  Inset Systems graphics - Hijaak
.IIF  Interchange File - QuickBooks for Windows 
.IL  Icon Library
.ima  Winimage compressed format (for ShrinkWrap)
.image  Mac disk image ;
.IMG  Image
.IND  Index
.INF  Information
.INI  Initialization - configuration settings
.IOB  Imagine file 
.ISU  Netscape file 
.IT  MOD music file format 
.IW  Idlewild screensaver 
.IX  Index File - Framemaker 
.JFF  JFIF, JPEG File Interchange Format
.JIF  JPEG Image Format 
.JPEG  JPEG bitmap 
.JPG  JPEG graphics file
.JT  JT Fax
.JTF  JPEG bitmap 
.KDC  Kodak Photo-Enhancer 
.KFX  Kofax
.LBL  Label - dBASE
.LBM  Deluxe Paint graphics file
.LDB  Lock file - Microsoft Access 
.LEG  Legacy document 
.lha  Filename extension for a PC/Amiga compression format
.lhs  Literate Haskell source file
.lhz  LHA compression file
.LIB  Library
.LIC  License file - shareware 
.LOG  Log
.LST  List 
.LWP  Lotus Word Pro document 
.LZH  LHARC compression
.lzs  PC/Amiga compression format
.M3D  Motion 3D - Corel 
.MAC  MacPaint
.MAF  Microsoft Access Form 
.MAK  Makefile
.MAM  Microsoft Access Macro 
.MAP  Map - linkage editor
.MAQ  Microsoft Access Query 
.MAR  Microsoft Access Report 
.MAT  Microsoft Access Table 
.MCS  MathCAD format
.MCW  Microsoft Word for Macintosh 
.MDB  Access database
.MDX  Multi-index
.MET  Metafile - OS/2
.MEU  Menu
.MFF  MIDI File Format 
.MGF  Micrografx Draw Font 
.MI  Miscellaneous 
.MIC  Microsoft Image Composer 
.MID  MIDI
.MIFF  An ImageMagick file format
.MIL  Group 4
.mime  MIME
.MME  Mime encoded file
.MMF  Microsoft Mail File 
.MMM  Macromind animation
.MOD  (music file format)
.MOV  Movie - QuickTime
.MOZ  Mozilla - Netscape cache file 
.MP3  MPEG compressed audio file
.MPE  MPEG 
.MPEG  MPEG compressed animation file 
.MPG  MPEG encoded file
.MPNT  Macintosh MacPaint
.MPP  Microsoft Project project file 
.MPT  Microsoft Project template file 
.MPX  Microsoft Project export file 
.MRK  Markup - Informative Graphics
.MSG  Message file
.MSN  Microsoft Network document 
.MSP  Microsoft Paint
.MUS  Music 
.MVB  Microsoft Multimedia Viewer 
.MYS  Myst saved game file 
.NDX  Index - dBASE
.NET  Network file 
.NG  Norton Guides
.NLM  NLM (Netware Loadable Module) program - NetWare
.NTF  Notes Template File - Lotus Notes database 
.OAB  Outlook Address Book - Microsoft 
.OAZ  OAZ Fax
.OBD  Microsoft Office Binder 
.OBJ  Object module
.OCX  Object Linking and Embedding (OLE) Custom Control 
.OLB  OLE Object Library 
.OLE  OLE object 
.ONX  Onyx Graphics Postershop 
.ORI  Original
.OVL  Overlay module
.OVR  Overlay module
.OZM  Sharp Organizer memo bank
.OZP  Sharp Organizer telephone bank
.P10  Tektronix Plot10
.PAB  Personal Address Book - Microsoft 
.PAK  Quake game data 
.PAL  Paintbrush palette 
.PAS  Pascal program file
.PAT  Pattern - Corel Draw 
.PBK  Microsoft Phonebook 
.PBM  Portable Bit Map
.PCD  Photo CD format
.PCL  HP LaserJet
.PCM  LaserJet cartridge information
.PCS  PICS animation 
.PCT  PC Paint
.PCW  PC Write
.PCX  PC Paintbrush ; Graphics file - Zsoft format
.PDF Portable Document Format
.PDG PrintShop Deluxe 
.PDV PC Paintbrush printer driver
.PFA Type 1 font - ASCII
.PFB Type 1 font - encrypted
.PFM Postscript Font Metrics; Windows Type 1 font metrics
.PGL HPGL 7475A plotter - vector graphics
.PGM Portable Gray Map bitmap 
.PHTML HTML document with preprocessing instructions (PPIs) 
.PIC PICT graphics format, or PIXAR picture file
.PICT Macintosh QuickDraw/PICT 
.PIF Program InformatiiPo
.USL  LaserJet landscape font
.USP  LaserJet portrait font
.uu  Uuencode compressed file
.uue  Uuencode file
.VBP  Visual Basic Project 
.VBX  Visual Basic Extension
.VDA  Targa bitmap 
.VGR  Ventura
.VIFF  Khoros Visualization image file
.VLB  Ventura Library 
.VOC  Sound Blaster
.VP  Ventura Publisher 
.VST  Targa bitmap 
.VUE  Relational View - dBASE
.VXD  Virtual Device Driver 
.WAB  Windows Address Book 
.WAV  Sound file
.WBK  Microsoft Word Backup 
.WDB  Microsoft Works Database 
.WID  Ventura width table 
.WIN  Windows backup file 
.WIZ  Microsoft Word Wizard 
.WK1  Lotus 1-2-3, up to 2.01
.WK3  Lotus version 3
.WK4  Lotus version 4
.WKQ  Quattro spreadsheet
.WKS  Lotus Worksheet ; Microsoft Works document 
.WLR VRML page
.WMF Windows Metafile
.WP WordPerfect
.WPD Windows Printer Description ; WordPerfect Demo ; WordPerfect Document 
.WPG WordPerfect Graphics
.WPM WordPerfect macro
.WPS Microsoft Works document
.WPT WordPerfect Template 
.WRI Windows Write document
.WRK Symphony spreadsheet
.WS1 WordStar for Windows 1 document 
.WS2 WordStar for Windows 2 document 
.WS3 WordStar for Windows 3 document 
.WS4 WordStar for Windows 4 document 
.WS5 WordStar for Windows 5 document 
.WS6 WordStar for Windows 6 document 
.WS7 WordStar for Windows 7 document 
.WVL Wavelet compressed bitmap 
.X AVS X image file
.XAR Corel Xara drawing 
.XBM X Bitmap
.XFX JetFax
.XIF Xerox Image Format 
.XLC Excel chart
.XLK Microsoft Excel backup 
.XLM Microsoft Excel macro 
.XLS Excel worksheet
.XLT Microsoft Excel template 
.XM MOD music format 
.XPM X Pixelmap
.XWD X Window System window dump image
.XXE Xxencoded file 
.YAL Arts & Letters click art
.Z Unix compress file
.ZIP File compressed using PKZIP
.ZOO Zoo compress file