Most computer users are familiar with file extensions, those alphanumeric characters that follow the file name and dot (e.g., "filename.txt"). If you've ever saved a word processing document or downloaded a picture from the Internet, you've probably noticed those extensions. While they may not seem important, extensions do help describe the contents of a file and making them compatible with other programs.
The file name extension serves several purposes. It allows a file's format to be described as a part of its name, so that users can quickly identify a particular type of file without having to open or use it. The extension also helps other applications, such as word processing programs and image editors, recognize whether the file being used is one that the application can work with.
In the file named ("chiropractic.doc"), the "doc" extension tells the user that the file is a Microsoft Word document without the user having to open the file and see what it is. It also lets the Microsoft Word application know that it is a file the program can open.
Some operating systems limit file extensions to only three characters. One nice feature of the Macintosh operating system is that it does not have a limit to its file extension system. This explains why some web pages have only a .htm extension, while others end with .html.
There are literally hundreds of file formats and extensions, and the list continues to grow. To help users identify what certain extensions mean, we've come up with this compendium of file name extensions that indicate the format or use of a file and a brief description of that format.
| Extension |
Description |
| ABK | Corel Draw AutoBackup |
| ACL | Corel Draw 6 keyboard accelerator |
| ACM | Used by Windows in the system directory |
| ACP | Microsoft Office Assistant Preview file |
| ACT | Microsoft Office Assistant Actor file |
| ACV | OS/2 drivers that compress and decompress data |
| AD | After Dark screen saver |
| ADB | Appointment database used by HP 100LX organizer |
| ADD | OS/2 adapter drivers used in the boot process |
| ADM | After Dark MultiModule screen saver |
| ADP | Used by FaxWorks for fax modem interaction |
| ADR | After Dark Randomizer screen saver |
| AF2, AF3 | ABC Flowchart file |
| AFM | Adobe font metrics |
| AI | Adobe Illustrator drawing |
| AIF | Apple Mac AIFF sound |
| ALB | JASC Image Commander album |
| ALL, YAL | Arts & Letters files |
| ANC | Canon Computer Pattern Maker file that is a selectable list of pattern colors |
| ANI | Animated cursor |
| ANS | ANSI text |
| API | Application Program Interface file |
| APR | Lotus Approach 97 file |
| APS | Microsoft Visual C++ file |
| ARC | LH ARC (old version) compressed archive |
| ARJ | Robert Jung ARJ compressed archive |
| ART | Xara Studio drawing (or) Canon Crayola art file |
| ASA | Microsoft Visual InterDev file |
| ASC | ASCII (a basic text file) |
| ASD | WinWord AutoSave |
| ASM | Assembler language source file |
| ASP | Active Server Page (an HTML file with a Microsoft server processed script) |
| ASP | Procomm Plus setup and connection script |
| AST | Claris Works "assistant" file |
| ATT | AT&T Group 4 bitmap |
| AVI | Microsoft Video for Windows movie |
| AWD | FaxView document |
| B4, LPD | Helix Nuts and Bolts file |
| BAK | Backup file |
| BAS | BASIC code |
| BAT | Batch file |
| BFC | Windows 95 Briefcase document |
| BI, BIN | Binary file |
| BIF | GroupWise initialization file |
| BK, BK$ | Sometimes used to denote backup versions |
| BKS | IBM BookManager Read bookshelf |
| BMP | Windows or OS/2 bitmap |
| BRX | A file for browsing an index of multimedia options |
| BTM | Batch file used by Norton Utilities |
| CAB | Microsoft cabinet file (program files compressed for software distribution) |
| CAL | CALS compressed bitmap (or) Calendar schedule data |
| CAS | Comma delimited ASCII file |
| CAT | IntelliCharge categorization file used by Quicken |
| CB | Microsoft clean boot file |
| CCB | Visual basic animated button configuration |
| CCF | Multimedia viewer configuration file used in OS/2 |
| CCH | Corel Chart |
| CCM | Lotus CC:Mail "box" (for example, inbox.ccm) |
| CDA | CD audio track |
| CDF | Microsoft Channel Definition Format file |
| CDI | Phillips Compact Disk Interactive format |
| CDR, CDT, CDX | Corel Draw files |
| CEL | CIMFast Event Language file |
| CFB | Compton's Multimedia file |
| CFG | Configuration file |
| CGI | Common gateway interface script file |
| CGM | Computer graphics metafile |
| CH | OS/2 configuration file |
| CHK | File fragments saved by Windows Disk Defragmenter or ScanDisk |
| CHP | Ventura Publisher chapter |
| CHT | ChartViewer file (or) Harvard Graphics vector file |
| CIL | Clip Gallery download package |
| CIN | OS/2 change control file that tracks changes to an INI file |
| CLASS | Java class |
| CLP | Windows Clipboard file |
| CLS | Visual basic class module |
| CMD | Command file for Windows NT (or) DOS CP/M command file (or) dBase II program file |
| CMF | Corel Metafile |
| CMP | JPEG bitmap (or) Address document |
| CMV | Corel Move animation |
| CMX | Corel Presentation Exchange image |
| CNF | Configuration file used by Telnet, Windows, and other applications with varying internal formats |
| CNM | Windows application menu options and setup file |
| CNQ | Compuworks Design Shop file |
| CNT | Windows (or other) system content files |
| COB | TrueSpace2 object |
| COD | Microsoft C compiler output |
| COM | Command file (program) |
| CPD, CPE | Fax Cover document |
| CPI | Microsoft MS DOS code page information file |
| CPL | Control Panel extension (or) Corel color palette |
| CPP | C++ code |
| CPR | Corel Presents presentation |
| CPT | Corel Photo Paint image |
| CPX | Corel Presentation Exchange compressed drawing |
| CRD | Cardfile file |
| CRP | Corel Presents run time presentation |
| CRT | Certificate file |
| CSC | Corel Script |
| CSP | PC Emcee on screen image |
| CSV | Comma separated values file |
| CT | Scitex CT bitmap |
| CTL | Used in general to mean a file containing control information |
| CUE | Microsoft Cue Cards data |
| CUR | Windows cursor |
| CUT | Dr. Halo bitmap |
| CV | Corel Versions archive (or) Microsoft CodeView information screen |
| CWK, CWS | Claris Works data files |
| CXX | C++ source code file |
| DAT | Data file (or) WordPerfect merge data |
| DBF | Aston Tate dBASE database |
| DBX | DataBeam image |
| DCR | Shockwave file |
| DCS | Desktop Color Separation file |
| DCX | Fax image (based on PCX) |
| DDF | BTRIEVE database |
| DEF | SmartWare II data file (or) C++ definition |
| DER | Certificate file |
| DIB | Device Independent Bitmap |
| DIC | Dictionary |
| DIF | Data Interchange Format spreadsheet |
| DIR | Macromedia Director file |
| DIZ | Description file |
| DLL | Dynamic Link Library |
| DOC | FrameMaker or FrameBuilder document (or) WordStar document (or) Microsoft Word document |
| DOT | Microsoft Word document template |
| DPR | Borland Delphi project header file |
| DRV | Driver |
| DRW | Micrografx Designer/Draw |
| DSP, DSW, | Microsoft Developer Studio files |
| DSQ | Corel QUERY file |
| DTF | Symantec Q&A relational database file |
| DXF | AutoDesk Drawing Interchange format |
| EMF | Enhanced Windows Metafile |
| ENC | Encore file |
| EPS | Encapsulated PostScript image |
| EVY | Envoy document |
| EWL | Microsoft Encarta document |
| EXE | Executable file (program) |
| Extension | Description |
| F, F77, FOR | Fortran file |
| FAR | Farandole Composer music module file |
| FAV | Microsoft Outlook navigation bar |
| FAX | FAX Type image |
| FH3 | Aldus Freehand 3 drawing |
| FIF | Fractal image file |
| FITS | CCD camera image |
| FLC, FLI | AutoDesk FLIC animation |
| FLT | Corel filter |
| FMB | Oracle binary source code for form, version 4.0 and later |
| FMT | Oracle text format of form, version 4.0 and later (or) Microsoft Schedule+ print file |
| FMX | Oracle executable form, version 4.0 and later |
| FOG | Fontographer font |
| FON | System font |
| FOT | Font related file |
| FP, FP3 | FileMaker Pro file |
| FPX | FlashPix bitmap |
| FRM | FramkeMaker or FrameBuilder document (or) Form (or) Visual Basic form (or) Wordperfect merge form |
| FRX | Visual Basic form stash file |
| GAL | Corel Multimedia Manager album |
| GCP | Ground Control Point files |
| GED | Graphic Environment Document (drawing) |
| GEM | GEM metafile |
| GEN | Ventura generated text file |
| GFC | Patton & Patton flowchart file |
| GFI, GFX, | Genigraphics Graphics Link presentation |
| GID | Windows 95 global index file |
| GIF | CompuServe bitmap |
| GIM, GIX, GNA, | |
| GNX, GWX, GWZ | |
| GRA | Microsoft graph |
| GRD | Grid file |
| GRP | Program Manager Group |
| GZ | Unix G-zip compressed file |
| H | C program header |
| HED | HighEdit document |
| HEX, HQX | Macintosh BinHex files |
| HGL | HP Graphics Language drawing |
| HLP | Help file |
| HPJ | Visual Basic Help Project |
| HPP | C++ program header |
| HST | History file |
| HT | HyperTerminal |
| HTM, HTML | Hypertext document |
| HTX | Extended HTML template |
| ICA | Citrix file |
| ICB, TGA, | Targa bitmap |
| ICM | Image Color Matching profile file |
| ICO | Windows icon |
| IDD | MIDI instrument definition |
| IDQ | Internet Data Query file |
| IDX | Symantec relational database index file |
| IFF | Amiga ILBM |
| IGF | Inset Systems metafile |
| IIF | QuickBooks for Windows interchange file |
| IMA | WinImage file |
| IMG | GEM image |
| INC | Assembler language or Active Server include file |
| INF | Information file |
| INI | Initialization file |
| INP | Oracle source code for version 3.0 and earlier |
| INS | InstallShield install script (or) X Internet sign up file |
| ISO | Lists the files on a CD ROM |
| ISP | X Internet sign up file |
| ISU | InstallShield uninstall script |
| IW | Idlewild screensaver |
| JAR | Java Archive file (a compressed file for applets and related files) |
| JAVA | Java source code |
| JBF | Paint Shop Pro image browser file |
| JFF, JIF, | JPEG image file |
| JMP | SAS JMP Discovery chart to stats file |
| JPEG, JPG, JTF | |
| JS | JavaScript source code |
| KDC | Kodak Photo Enhancer |
| KFX | KoFax Group 4 image |
| LBM | Deluxe Paint bitmap |
| LDB | Microsoft Access lock file |
| LEG | Legacy document |
| LHA, LZH | LH ARC compresed archive |
| LIB | Library file |
| LIS | Output file produced by a Structured Query Reporting (SQR) program |
| LOG | Log file |
| LRC | Intel Video Phone file |
| LST | List file |
| LWO | Lightwave Object file |
| LWP | Lotus WordPro 96/97 file |
| LZS | Skyroads data file |
| M3D | Corel Motion 3D animation |
| MAC | MacPaint image |
| MAD, MAF, | Microsoft Access files |
| MAK | Visual Basic or MS Visual C++ Project |
| MAM, MAQ, MAR, | |
| MAP | Map file |
| MAS | Lotus Freelance Smartmaster file |
| MAT, MDA, MDB, | |
| MAX | Paperport file |
| MAZ | Hover maze data |
| MCC | Dialer10 calling card |
| MCS | MathCAD image |
| MCW | Microsoft Word for Macintosh document |
| MDE, MDN, MDW | |
| MER | Format for interchanging spreadsheet/database data; recognized by Filemaker, Excel, and others |
| MET | Presentation Manager metafile |
| MI | Miscellaneous |
| MIC | Microsoft Image Composer file |
| MID | MIDI music |
| MMF | Microsoft Mail file |
| MMM | Microsoft multimedia movie |
| MOD | FastTracker, StarTrekker, Noise Tracker (etc.) music module file |
| MOV | QuickTime for Windows movie |
| MP3 | MPEG Audio Layer 3 (AC3) file |
| MPE, MPEG, | MPEG animation |
| MPG | |
| MPP | Microsoft Project file (or) CAD file format |
| MSG | Microsoft Mail message |
| MSN | Microsoft Network document |
| MSP | Microsoft Paint bitmap |
| MUS | Music file |
| MVB | Microsoft Multimedia Viewer file |
| MWP | Lotus Wordpro 97 Smartmaster file |
| NAP | NAP Metafile (vector image) |
| NCB, OPT | |
| NSF, NTF | Lotus Notes files |
| OBD, OBZ | Microsoft Office Binder file |
| OBJ | Object file |
| OCX | Microsoft Object Linking and Embedding custom control |
| OFN | Microsoft Office FileNew file |
| OFT | Microsoft Outlook template |
| OLB, OLE | OLE Object files |
| ORG, OR2, OR3 | Lotus Organizer file |
| P10 | Tektronix Plot 10 drawing |
| PAB | Microsoft personal address book |
| PAL | Windows color palette |
| PAT | Corel Draw pattern |
| PBK | Microsoft Phonebook |
| PBM | Portable Bitmap |
| PCD | Kodak Photo CD image |
| PCL | HP Laserjet bitmap |
| PCS | PICS animation |
| PCT | Macintosh PICT drawing |
| PCX | ZSoft PC Paintbrush bitmap |
| PDF | Adobe Acrobat Portable Document Format (or) Netware Printer Definition File |
| PFA, PFB | Type 1 font file |
| PFC | PF component |
| PFM | Printer font metrics |
| PGL | HP Plotter drawing |
| PGM | Portable graymap (bitmap) |
| PIC | PC Paint bitmap (or) Lotus picture (or) Macintosh PICT drawing |
| PIF | Program information file (or) IBM PIF drawing |
| PIX | Inset Systems bitmap |
| PJ | MKS source integrity file |
| PKG | Microsoft Developer Studio application extension |
| PL | Perl program |
| PLT | HPGL Plotter drawing (or) AutoCAD Plot drawing |
| PM5, PM6, P65 | Pagemaker 5.0-6.5 files |
| PNG | Portable Network Graphics bitmap |
| PNT | MacPaint graphic file |
| POT, PPA, | Microsoft PowerPoint files |
| PP4 | Picture Publisher 4 bitmap |
| PPM | Portable pixelmap bitmap |
| PPS, PPT | |
| PRE | Lotus Freelance presentation |
| PRF | Windows system file |
| PRN | Print table (space delimited text) |
| PRS | Harvard Graphics for Windows presentation |
| PRZ | Lotus Freelance Graphics 97 file |
| PS | Postscript interpreted drawing |
| PSD | Adobe Photoshop bitmap |
| PST | Microsoft Outlook personal folder file |
| PUB | Ventura Publisher publication (or) Microsoft Publisher document |
| QAD | PF QuickArt document |
| QBW | QuickBooks for Windows file |
| QLB | Quick Library |
| QRY | Microsoft Query |
| QT, QTM | QuickTime Movie |
| QXD | Quark XPress file |
| R | Pegasus Mail resource file |
| RA, RAM | Real Audio sound |
| RAS | Sun Raster Images bitmap |
| RAW | Raw File Format (bitmap) |
| REG | Registration file |
| RLE | Run length encoded bitmap |
| RM | Real Audio video file |
| RMI | MIDI music |
| ROV | Rescue Rover data file |
| RTF | Rich Text Format document |
| SAM | Ami Professional document |
| SAV | Saved game file |
| SCC | Microsoft Source Safe file |
| SCD, SCH, SC2 | Microsoft Schedule+ file |
| SCP | Dial Up Networking Script |
| SCR | Windows screen saver (or) fax image |
| SCT | Scitex CT bitmap |
| SDL, SDR, SDT | SmartDraw files |
| SEA | Self expanding archive |
| SEP | Tagged Image File Format (TIFF) bitmap |
| SHB | Corel Show presentation (or) document shortcut file |
| SHG | Hotspot bitmap |
| SHS | Shell scrap file |
| SHW | Corel Show presentation |
| SIT | Stuffit archive of Mac files |
| SLK | Symbolic Link (SYLK) spreadsheet |
| SND | Next sound (or) Mac sound resource |
| SQC | Structured Query Language (SQR) file |
| STY | Ventura Publisher style sheet |
| SVX | Amiga 8SVX sound |
| SYS | System file |
| TAR | Tape Archive |
| TAZ, TGZ | Unix Gzip/Tape Archive |
| TEX | Texture file |
| THEME | Windows 95 desktop theme |
| THN | Graphics Workshop for Windows thumbnail |
| TIF, TIFF | Tag Image File Format (TIFF) bitmap |
| TLB | OLE type library |
| TMP | Windows temporary file |
| TRM | Terminal file |
| TRN | MKS Source Integrity project usage log |
| TTF | TrueType font |
| TWF | TabWorks file |
| TX8 | MS DOS Text |
| TXT | Text file |
| UDF | Windows NT Uniqueness Database file |
| URL | Internet shortcut |
| USE | MKS source integrity file |
| VBP, VBX | Visual Basic files |
| VBW | Microsoft Visual Basic workspace |
| VDA, VST | |
| VI | Virtual instrument file |
| VLB | Corel Ventura library |
| VOC | Creative Labs Sound Blaster sound file |
| VP | Ventura Publisher publication |
| VSD, VSW | Visio Workspace file |
| VXD | Microsoft Windows virtual device driver |
| WAV | Windows Waveform sound |
| WB1, WB2 | QuattroPro for Windows spreadsheet |
| WBK | Microsoft Word backup |
| WBL | Argo WebLoad II upload file |
| WCM | WordPerfect macro |
| WDB | Microsoft Works database |
| WEB | CorelXara Web document |
| WID | Ventura width table |
| WIL | WinImage file |
| WIZ | Microsoft Word wizard |
| WK1, WK3, WK4 | Lotus 123 spreadsheet files |
| WKS | Lotus 123 Worksheet spreadsheet (or) Microsoft Works document |
| WLL | Microsoft Word Add In |
| WMF | Windows Metafile |
| WP, WPD, | WordPerfect document |
| WP4, WP5, WP6 | |
| WPG | WordPerfect graphic |
| WPS | Microsoft Works document |
| WPT | WordPerfect template |
| WPW | Novel PerfectWorks document |
| WQ1, WQ2 | QuattroPro/DOS spreadsheet |
| WRI | Write document |
| WRL | Virtual Reality model |
| WS1, WS2, | WordStar for Windows document |
| WS3, WS4, WS5, | |
| WS6, WS7 | |
| WSD | WordStar 2000 document |
| WVL | Wavelet compressed bitmap |
| XAR | Corel Xara drawing |
| XLA, XLB, | Microsoft Excel related files |
| XLC, XLD, XLK, | |
| XLM, XlS, XLT, | |
| XLV, XLW | |
| XM | FastTracker 2, Digital Tracker music module file |
| XTP | XTree data file |
| XY3, XY4, | XYWrite documents |
| XYP, XYW | |
| YBK | Microsoft Encarta yearbook |
| Z | Unix Gzip compressed file |
| ZIP | Zip file compressed archive |
| 000 999 | Used to number backup versions of files; also used to number data files for multiple users of a small scale PC application |
| 12M, 123 | Lotus 123 files |
| 2GR, 3GR | VGA graphics driver/configuration files |
| 386 | A file used in an 80386 or higher microprocessor |
| #01 and higher | A method of numbering picture files for film that has been scanned onto a PC |
| $$$ | Used by OS/2 to track archived files |
As always, we welcome your comments. If you have any questions about the file formats mentioned above, feel free to contact me at the e-mail address listed below.
