Trying to find out what application uses a particular file extension? Here is a quick table of some of the more common file extensions, as well as their associated applications.
| 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 audio data |
| AD | After Dark screensaver |
| ADB | Appointment database used by HP 100LX organizer |
| ADD | OS/2 adapter drivers used in the boot process |
| ADM | After Dark MultiModule screensaver |
| ADP | Used by FaxWorks to do setup for fax modem interaction |
| ADR | After Dark Randomizer screensaver |
| AFM | Adobe font metrics |
| AF2 | ABC Flowchart file |
| AF3 | ABC Flowchart file |
| AI | Adobe Illustrator drawing |
| AIF | Apple Mac AIFF sound |
| ALB | JASC Image Commander album |
| ALL | Arts & Letters Library |
| AMS | Velvert Studio music module (MOD) file |
| 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; used by Adobe Acrobat |
| 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 |
| ART | Canon Crayola art file |
| ASA | Microsoft Visual InterDev file |
| ASC | ASCII text |
| ASD | WinWord AutoSave |
| ASM | Assembler language source file |
| ASP | Active Server Page (an HTML file containing 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 |
| BAK | Backup file |
| BAS | BASIC code |
| BAT | Batch file |
| BFC | Windows 95 Briefcase document |
| BG | Backgammon for Windows game |
| BI | Binary file |
| BIF | GroupWise initialization file |
| BIN | Binary file |
| BK | Sometimes used to denote backup versions |
| BK$ | Also sometimes used to denote backup versions |
| BKS | An IBM BookManager Read bookshelf |
| BMK | An A bookmark file |
| BMP | Windows or OS/2 bitmap |
| BM1 | Apogee BioMenace data file |
| BRX | A file for browsing an index of multimedia options |
| BSP | Quake map |
| BS1 | Apogee Blake Stone data file |
| BTM | Batch file used by Norton Utilities |
| B4 | Helix Nuts and Bolts file |
| C | C code |
| CAB | Microsoft cabinet file (program files compressed for software distribution) |
| CAL | CALS Compressed Bitmap |
| CAL | 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 | Core Draw drawing |
| CDT | Corel Draw template |
| CDX | Corel Draw compressed drawing |
| CEL | CIMFast Event Language file |
| CFB | Comptons 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 |
| CIL | Clip Gallery download package |
| CIM | Sim City 200 file |
| CIN | OS/2 change control file that tracks changes to an INI file |
| CK1 | iD/Apogee Commander Keen 1 data file |
| CK2 | iD/Apogee Commander Keen 2 data file |
| CK3 | iD/Apogee Commander Keen 3 data file |
| CK4 | iD/Apogee Commander Keen 4 data file |
| CK5 | iD/Apogee Commander Keen 5 data file |
| CK6 | iD/Apogee Commander Keen 6 data file |
| CLASS | Java class |
| CLP | Windows Clipboard file |
| CLS | Visual Basic Class Module |
| CMD | Command file for Windows NT (similar to a DOS .BAT file) |
| CMD | DOS CP/M command file |
| CMD | dBase-II program file |
| CMF | Corel Metafile |
| CMP | JPEG Bitmap |
| CMP | Address document |
| CMV | Corel Move animation |
| CMX | Corel Presentation Exchange image |
| CNF | Configuration file used by Telnet, Windows, and other applications |
| CNM | Windows application menu options and setup file |
| CNQ | Compuworks Design Shop file |
| CNT | Windows (or other) system content files for the help index and other purposes |
| COB | trueSpace2 object |
| COD | Microsoft C compiler output as displayable assembler with original C as comments |
| COM | Command file (program) |
| CPD | Fax Cover document |
| CPE | Fax Cover document |
| CPI | Microsoft MS-DOS code page information file |
| CPL | Control Panel extension |
| CPL | Corel colour 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 |
| CV | Microsoft CodeView information screen |
| CWK | Claris Works data file |
| CWS | Claris Works template |
| CXX | C++ source code file |
| DAT | Data file |
| DAT | 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 |
| DEF | C++ Definition |
| DER | Certificate file |
| DIB | Device-Independent Bitmap |
| DIC | Dictionary |
| DIF | Data Interchange Format spreadsheet |
| DIR | Macromedia Director file |
| DIZ | Description file |
| DLG | C++ Dialogue Script |
| DLL | Dynamic-Link Library |
| DMF | X-Trakker music module (MOD) file |
| DOC | FrameMaker or FrameBuilder document |
| DOC | WordStar document |
| DOC | WordPerfect document |
| DOC | Microsoft Word document |
| DOT | Microsoft Word document Template |
| DPR | Borland Delphi project header file |
| DRV | Driver |
| DRW | Micrografx Designer/Draw |
| DSG | DooM saved game |
| DSM | Dynamic Studio music module (MOD) file |
| DSP | Microsoft Developer Studio project |
| DSQ | Corel QUERY file |
| DSW | Microsoft Developer Studio workspace |
| DWG | AutoCAD drawing eXchange format |
| DXF | AutoDesk Drawing Interchange format |
| EMF | Enhanced Windows Metafile |
| ENC | Encore file |
| EPS | Encapsulated PostScript image |
| ER1 | ERWin file |
| ERX | ERWin file |
| EVY | Envoy document |
| EWL | Microsoft Encarta document |
| EXE | Executable file (program) |
| F | FORTRAN file |
| F77 | FORTRAN file |
| F90 | FORTRAN file |
| FAR | Farandole Composer music module (MOD) file |
| FAV | Microsoft Outlook navigation bar |
| FAX | FAX Type image |
| FH3 | Aldus Freehand 3 drawing |
| FIF | Fractal image file |
| FITS | CCD camera image |
| FLC | AutoDesk FLIC animation |
| FLI | AutoDesk FLIC animation |
| FLT | Corel filter |
| FLT | StarTrekker music module (MOD) file |
| FMB | Oracle binary source code for form, version 4.0 and later |
| FMT | Oracle text format of form, version 4.0 and later |
| FMT | Microsoft Schedule+ print file |
| FMX | Oracle executable form, version 4.0 and later |
| FOG | Fontographer font |
| FON | System font |
| FOR | FORTRAN file |
| FOT | Font-related file |
| FP | FileMaker Pro file |
| FP1 | Flying Pigs for Windows data file |
| FP3 | FileMaker Pro file |
| FPX | FlashPix bitmap |
| FRM | Form |
| FRM | FrameMaker or FrameBuilder document |
| FRM | Oracle executable form version 3.0 and earlier |
| FRM | Visual Basic form |
| FRM | WordPerfect Merge form |
| FRX | Visual Basic form stash file |
| GAL | Corel Multimedia Manager album |
| GCP | Ground Control Point file used in image processing of remote sensing data . |
| GED | Graphic Environment Document (drawing) |
| GEM | GEM metafile |
| GEN | Ventura-Generated text file |
| GFC | Patton&Patton Flowcharting 4 flowchart file |
| GFI | Genigraphics Graphics Link presentation |
| GFX | Genigraphics Graphics Link presentation |
| GID | Windows 95 global index file (containing help status) |
| GIF | CompuServe bitmap |
| GIM | Genigraphics Graphics Link presentation |
| GIX | Genigraphics Graphics Link presentation |
| GNA | Genigraphics Graphics Link presentation |
| GNX | Genigraphics Graphics Link presentation |
| GRA | Microsoft Graph |
| GRD | Grid file, used in image processing of remote sensing data often to form map projections. |
| GRP | Program Manager Group |
| GTK | Graoumftracker (old) music module (MOD) file |
| GT2 | Graoumftracker (new) music module (MOD) file |
| GWX | Genigraphics Graphics Link presentation |
| GWZ | Genigraphics Graphics Link presentation |
| GZ | Unix Gzip compressed file |
| H | C program header |
| HED | HighEdit document |
| HEL | Microsoft Hellbender saved game |
| HEX | Macintosh BinHex 2.0 file |
| HGL | HP Graphics Language drawing |
| HLP | Help file |
| HOG | Lucas Arts Dark Forces WAD file |
| HPJ | Visual Basic Help Project |
| HPP | C++ program header |
| HQX | Macintosh BinHex 4.0 file |
| HST | History file |
| HT | HyperTerminal |
| HTM | Hypertext document |
| HTML | Hypertext document |
| HTX | Extended HTML template |
| ICA | Citrix file |
| ICB | Targa bitmap |
| ICM | Image Color Matching profile file |
| ICO | Windows Icon |
| IDD | MIDI Instrument Definition |
| IDQ | Internet Data Query 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 form, version 3.0 and earlier |
| INS | InstallShield install script |
| INS | X-Internet sign-up file |
| ISO | Lists the files on a CD-ROM; based on the ISO 9660 CD-ROM file system standard |
| ISP | X-Internet sign-up file |
| ISU | InstallShield uninstall script |
| IT | Impulse Tracker music module (MOD) file |
| 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 | JPEG bitmap |
| JIF | JPEG bitmap |
| JMP | SAS JMPDiscovery chart-to-statistics file |
| JN1 | Epic MegaGames Jill of the Jungle data file |
| JPEG | JPEG bitmap |
| JPG | JPEG bitmap |
| JS | JavaScript source code |
| JTF | JPEG bitmap |
| KDC | Kodak Photo-Enhancer |
| KFX | KoFax Group 4 image |
| KYE | Kye game data |
| LBM | Deluxe Paint bitmap |
| LDB | Microsoft Access lock file |
| LEG | Legacy document |
| LHA | Alternate file suffix for LZH |
| LIB | Library |
| LIS | Output file produced by a Structured Query Reporting (SQR) program |
| LOG | 1. Log file |
| LOG | 2. Log file used by pokerstars for errors in their poker software |
| LPD | Helix Nuts and Bolts file |
| LRC | Intel Video Phone file |
| LST | List file |
| LWO | Lightwave Object file |
| LWP | Lotus Wordpro 96/97 file |
| LZH | LH ARC compressed archive |
| LZS | Skyroads data file |
| M3D | Corel Motion 3D animation |
| MAC | MacPaint image |
| MAD | Microsoft Access module |
| MAF | Microsoft Access Form |
| MAK | Visual Basic or MS Visual C++ Project |
| MAM | Microsoft Access Macro |
| MAP | Map file |
| MAP | Duke Nukem 3D WAD game file |
| MAQ | Microsoft Access Query |
| MAR | Microsoft Access Report |
| MAS | Lotus Freelance Graphics Smartmaster file |
| MAT | Microsoft Access Table |
| MAX | Paperport file |
| MAZ | Hover maze data |
| MB1 | Apogee Monster Bash data file |
| MCC | Dialer10 calling card |
| MCS | MathCAD image |
| MCW | Microsoft Word for Macintosh document |
| MDA | Microsoft Access add-in |
| MDB | Microsoft Access database |
| MDE | Microsoft Access MDE file |
| MDL | Digital Tracker music module (MOD) file |
| MDL | Quake model file |
| MDN | Microsoft Access blank database template |
| MDW | Microsoft Access Workgroup |
| MDZ | Microsoft Access wizard template |
| MED | Music Editor, OctaMED music module (MOD) file |
| 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 |
| MOD | Microsoft Multiplan spreadsheet |
| MOV | QuickTime for Windows movie |
| MPE | MPEG animation |
| MPEG | MPEG animation |
| MPG | MPEG animation |
| MPP | Microsoft Project file |
| MPP | CAD drawing file format |
| MP3 | MPEG Audio Layer 3 (AC3) file |
| MSG | Microsoft Mail message |
| MSN | Microsoft Network document |
| MSP | Microsoft Paint bitmap |
| MTM | MultiTracker music module (MOD) file |
| MUS | Music |
| MVB | Microsoft Multimedia Viewer file |
| MWP | Lotus Wordpro 97 Smartmaster file |
| NAP | NAP Metafile |
| NCB | Microsoft Developer Studio file |
| NSF | Lotus Notes database |
| NST | Noise Tracker music module (MOD) file |
| NTF | Lotus Notes database template |
| OBD | Microsoft Office binder template |
| OBD | Microsoft Office Binder |
| OBJ | Object file |
| OBZ | Microsoft Office Binder Wizard |
| OCX | Microsoft Object Linking and Embedding custom control |
| OFN | Microsoft Office FileNew file |
| OFT | Microsoft Outlook template |
| OKT | Oktalyzer music module (MOD) file |
| OLB | OLE Object Library |
| OLE | OLE object |
| OPT | Microsoft Developer Studio file |
| ORG | Lotus Organiser file |
| OR2 | Lotus Organiser 2 file |
| OR3 | Lotus Organiser 97 file |
| P10 | Tektronix Plot 10 drawing |
| PAB | Microsoft Personal Address Book |
| PAK | Quake WAD file |
| PAL | Windows colour 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 |
| Adobe Acrobat Portable Document Format or Netware Printer Definition File | |
| Package Definition File from Microsoft Systems Management Server | |
| PDQ | Patton&Patton Flowcharting PDQ Lite file |
| PFA | Type 1 font (ASCII) |
| PFB | Type 1 font (binary) |
| PFC | PF Component |
| PFM | Printer Font Metrics |
| PGL | HP Plotter drawing |
| PGM | Portable Graymap (bitmap) |
| PIC | PC Paint bitmap |
| PIC | Lotus picture |
| PIC | Macintosh PICT drawing |
| PIF | Program Information File |
| PIF | IBM PIF drawing |
| PIG | Lucas Arts Dark Forces WAD file |
| PIN | Epic Pinball data file |
| PIN | Epic Pinball data file |
| PIX | Inset Systems bitmap |
| PJ | MKS Source Integrity file |
| PKG | Microsoft Developer Studio application extension (similar to a DLL file) |
| PL | Perl program |
| PLT | HPGL Plotter drawing |
| PLT | AutoCAD Plot drawing |
| PM5 | Pagemaker 5.0 file |
| PM6 | Pagemaker 6.0 file |
| P65 | Pagemaker 6.5 file |
| PNG | Portable Network Graphics bitmap |
| PNG | Paint Shop Pro Browser catalogue |
| PNT | MacPaint graphic file |
| POT | Microsoft PowerPoint Template |
| PP4 | Picture Publisher 4 bitmap |
| PPA | Microsoft PowerPoint Add-in |
| PPM | Portable Pixelmap bitmap |
| PPS | Microsoft PowerPoint slide show |
| PPT | Microsoft PowerPoint presentation |
| 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 |
| PTM | Polytracker music module (MOD) file |
| PUB | Ventura Publisher publication |
| PUB | Microsoft Publisher document |
| PWD | Microsoft Pocket Word document |
| PWZ | Microsoft PowerPoint Wizard |
| PXL | Microsoft Pocket Excel spreadsheet |
| QAD | PF QuickArt Document |
| QBW | QuickBooks for Windows file |
| QDT | Quick Books data file from the Quicken UK Accountancy/Tax/Invoice program |
| QLB | Quick Library |
| QRY | Microsoft Query |
| QT | QuickTime Movie |
| QTM | QuickTime Movie |
| QXD | Quark XPress file |
| R | Pegasus Mail resource file |
| RA | Real Audio sound |
| RAM | Real Audio sound |
| RAS | Sun Raster Images bitmap |
| RAW | Raw File Format (bitmap) |
| RC | Microsoft Visual C++ Resource Script |
| REC | Recorder macro |
| REG | Registration file |
| RES | Microsoft Visual C++ Resource |
| RFT | RFT-DCA |
| RLE | Run-Length Encoded bitmap |
| RM | Real Audio video file |
| RMI | MIDI music |
| ROV | Rescue Rover data file |
| RPT | Microsoft Visual Basic Crystal Reports file |
| RTF | Rich Text Format document |
| RTM | Real Tracker music module (MOD) file |
| SAM | Ami Professional document |
| SAV | Saved game file |
| SCC | Microsoft Source Safe file |
| SCD | Matrix/Imapro SCODL slide image |
| SCD | Microsoft Schedule+ 7 |
| SCH | Microsoft Schedule+ 1 |
| SCN | trueSpace2 scene |
| SCP | Dial-Up Networking Script |
| SCR | Windows screensaver |
| SCR | Fax image |
| SCT | Scitex CT bitmap |
| SC2 | Microsoft Schedule+ 7 |
| SDL | SmartDraw library |
| SDR | SmartDraw drawing |
| SDT | SmartDraw template |
| SEA | Self-expanding archive (used by Stuffit for Mac files and possibly by others) |
| SEP | Tagged Image File Format (TIFF) bitmap |
| SHB | Corel Show presentation |
| SHB | 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 |
| SND | Mac Sound Resource |
| SQC | Structured Query Language (SQR) common code file |
| SQR | Structured Query Language (SQR) program file |
| STM | Scream Tracker music module (MOD) file |
| STY | Ventura Publisher style sheet |
| SVX | Amiga 8SVX sound |
| SYS | System file |
| S3M | Scream Tracker 3 music module (MOD) file |
| TAR | Tape Archive |
| TAZ | Unix Gzip/Tape Archive |
| TEX | Texture file |
| TGA | Targa bitmap |
| TGZ | Unix Gzip/Tape Archive |
| THEME | Windows 95 Desktop Theme |
| THN | Graphics Workshop for Windows thumbnail |
| TIF | Tag Image File Format (TIFF) bitmap |
| TIFF | Tag Image File Format (TIFF) bitmap |
| TIG | Tiger file, used by US government to distribute maps |
| TLB | OLE Type Library |
| TMP | Windows temporary file |
| TRM | Terminal file |
| TRN | MKS Source Integrity project usage log |
| TTF | TrueType font |
| TWF | TabWorks file |
| TWW | Tagwrite Template |
| TX8 | MS-DOS Text |
| TXT | Text |
| T2T | Sonata CAD modelling software file |
| UDF | Windows NT Uniqueness Database File |
| ULT | Ultratracker music module (MOD) file |
| URL | Internet shortcut |
| USE | MKS Source Integrity file |
| VBP | Visual Basic Project |
| VBW | Microsoft Visual Basic workspace |
| VBX | Visual Basic custom control |
| VCF | Vevi Configuration File; defines objects for use with Sense8’s WorldToolKit |
| VDA | Targa bitmap |
| VI | Virtual Instrument file from National Instruments LABView product |
| VLB | Corel Ventura Library |
| VOC | Creative Labs Sound Blaster sound |
| VP | Ventura Publisher publication |
| VSD | Visio drawing (flow chart or schematic) |
| VST | Targa bitmap |
| VSW | Visio Workspace file |
| VXD | Microsoft Windows virtual device driver |
| WAD | Large file for Doom game containing video, player level, and other information |
| WAV | Windows Waveform sound |
| WB1 | QuattroPro for Windows spreadsheet |
| 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 |
| WGP | Wild Board Games data file |
| WID | Ventura width table |
| WIL | WinImage file |
| WIZ | Microsoft Word Wizard |
| WK1 | Lotus 123 versions 1 & 2 spreadsheet |
| WK3 | Lotus 123 version 3 spreadsheet |
| WK4 | Lotus 123 version 4 spreadsheet |
| WKS | Lotus 123 Worksheet spreadsheet |
| WKS | Microsoft Works document |
| WLF | Argo WebLoad I upload file |
| WLL | Microsoft Word Add-In |
| WMF | Windows Metafile |
| WOW | Grave Composer music module (MOD) file |
| WP | WordPerfect document |
| WPW | Novel PerfectWorks document |
| WP4 | WordPerfect 4 document |
| WP5 | WordPerfect 5 document |
| WP6 | WordPerfect 6 document |
| WPD | WordPerfect Demo |
| WPD | WordPerfect Document |
| WPG | WordPerfect Graphic |
| WPS | Microsoft Works document |
| WPT | WordPerfect Template |
| WQ1 | QuattroPro/DOS spreadsheet |
| WQ2 | QuattroPro/DOS version 5 spreadsheet |
| WRI | Write document |
| WRL | Virtual Reality model |
| 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 |
| WSD | WordStar 2000 document |
| WVL | Wavelet Compressed Bitmap |
| XAR | Corel Xara drawing |
| XLA | Microsoft Excel add-in |
| XLB | Microsoft Excel toolbar |
| XLC | Microsoft Excel chart |
| XLD | Microsoft Excel dialogue |
| XLK | Microsoft Excel backup |
| XLM | Microsoft Excel macro |
| XLS | Microsoft Excel worksheet |
| XLT | Microsoft Excel template |
| XLV | Microsoft Excel VBA module |
| XLW | Microsoft Excel workbook / workspace |
| XM | FastTracker 2, Digital Tracker music module (MOD) file |
| XR1 | Epic MegaGames Xargon data file |
| XTP | XTree data file |
| XY3 | XYWrite III document |
| XY4 | XYWrite IV document |
| XYP | XYWrite III Plus document |
| XYW | XYWrite for Windows 4.0 document |
| YAL | Arts & Letters clipart library |
| YBK | Microsoft Encarta Yearbook |
| Z | Unix Gzip |
| ZIP | Zip file |
| ZOO | An early compressed file format |
| 000-999 | Used to number old versions of files and number related data files |
| 12M | Lotus 123 97 Smartmaster file |
| 123 | Lotus 123 97 file |
| 2GR and 3GR | VGA Graphics driver/configuration files under Windows |
| 386 | A file for use in an 80386 or higher microprocessor |
| 669 | Composer 669, Unis Composer music mod file |
| #01 and higher | A method of numbering picture files for a roll of film that has been scanned |
| $$$ | Used by OS/2 to keep track of archived files |
| @@@ | Screen files used in the installation and instruction on use of applications |