A

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

B


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     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

D


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

E


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


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

G

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

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

I


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

J 

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

K


KDC     Kodak Photo-Enhancer
KFX     KoFax Group 4 image
KYE     Kye game data

L


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

M


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

N


NAP     NAP Metafile
NCB     Microsoft Developer Studio file
NSF     Lotus Notes database
NST     Noise Tracker music module (MOD) file
NTF     Lotus Notes database template

O


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

P


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
PDF     Adobe Acrobat Portable Document Format or Netware Printer Definition File
PDF     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

Q


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


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

S


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

T


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

U


UDF     Windows NT Uniqueness Database File
ULT     Ultratracker music module (MOD) file
URL     Internet shortcut
USE     MKS Source Integrity file

V


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

W


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

X


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

Y


YAL     Arts & Letters clipart library
YBK     Microsoft Encarta Yearbook

Z 

Z     Unix Gzip
ZIP     Zip file
ZOO     An early compressed file format