Common Filename Extensions

Appendix. Common Filename Extensions

This appendix lists many of the most common filename extensions that you'll find on your system, that you might download, or that you have received over the Internet.

Extensions were universally used on DOS and Windows 3.1 files, but Microsoft has gone to some difficulty to hide them in Windows Vista. This is unfortunate, because they play a major role in the way Windows decides what application will be used to open a file, as well as which files will be visible when opening files in a given application. Although direct associations are made between some files without extensions and the applications needed to open them, in most cases the association is between an extension and a Registry setting that tells the system what application to use. To enable the display of filename extensions, open Windows Explorer, go to Control Panel [Appearance and Personalization] Folder Options View tab, and turn off the "Hide extensions for known file types option.

If you double-click on an unknown file type, the Open With dialog box appears, allowing you to make a new association. To subsequently change an association once it has been made, right-click on the file and select Open With, or select Properties and then click Change.

Table D-1 list many system extensions, but third-party applications use literally thousands of file formats. And you might be thrown off by an improperly named file, or by an application using a standard filename extension for a nonstandard purpose. You can open many of these file types only if you have the appropriate application. If all else fails, you can open just about any file in Notepad; although nontext files will look mostly like gibberish, you may get clues in some of the excerpts of readable text you'll see.

If you still can't find a file's type from its extension, there are several more good sources:

• Microsoft has put together a simple "extension finder" web site, intended for use with the "Use the Web service to find the correct program" feature that appears when you try to open a file with an extension that Windows doesn't recognize. The address for this site is:

  http://shell.windows.com/fileassoc/0409/xml/redir.asp?Ext={your extension}

  where {your extension} is the filename extension (without the dot) that you want to learn more about. For example, to find out about the .sit extension, you'd go to:

  http://shell.windows.com/fileassoc/0409/xml/redir.asp?Ext=sit

• Use an ordinary search engine such as Google (http://www.google.com) to search for references to the filename extension. For example, to find out about the .hqx extension, try searching for "hqx file" (with the quotes).

Table D-1. Common filename extensions

Extension	Description
.$$$	Temporary file
.1st	ASCII text file (e.g., READ.1st)
.3ds	3D Studio file
.3gp, .3gpp	Video clip created on a cell phone or other mobile device
.3gr	Windows Video Grabber datafile
.8m	PageMaker Printer font with Math 8 extended character set
.8u	PageMaker Printer font with Roman 8 extended character set
.abf	Adobe Binary Font
.abm	Photo album
.abs	MPEG audio sound file
.aca	Microsoft Agent Character file
.ace	Ace Archiver compressed file
.acf	Microsoft Agent Character file
.ad	AfterDark screensaver
.adi	AutoCAD graphics
.adx	Archetype designer document
.afi	Truevision bitmap graphics
.afm	ATM Type 1 font metric ASCII data for font installer
.ai	Adobe Illustrator vector graphics
.ans	ANSI graphics; character animation
.aps	Microsoft Visual C++ file
.arc	Compressed file archive
.arf	Automatic Response File
.arj	Compressed file archive created by ARJ
.asc	ASCII text file
.ascx	Microsoft ASP.NET user control file
.asd	Word for Windows Autosave file
.asm	Assembly source code file
.asmx	Microsoft .NET Web Service file
.asp	Microsoft Active Server Page
.aspx	Microsoft ASP.NET file
.asx	Microsoft Windows Media Active Stream Redirector file
.asx	Windows Media Streaming video shortcut
.atm	Adobe Type Manager data/information
.au	Audio file used on older web pages
.avi	Video for Windows Audio Video Interleaved movie clip
.awm	Animation Works movie
.b3d	3D Builder file
.bak	Backup file (generic)
.bas	Basic source code file
.bat	DOS batch file
.bco	Bitstream Outline font description
.bdr	Microsoft Publisher Border
.bez	Bitstream Outline font description
.bga	Bitmap graphics
.bib	Bibliography (ASCII)
.bin	Binary file
.bit	Bitmap X11
.bkf	Microsoft backup file
.bkw	FontEdit mirror image of font set
.bm	Bitmap graphics
.bmf	Corel image file
.bmp	Windows bitmap
.bsc	Microsoft Fortran Pwbrmake object file
.bup	Backup file (generic)
.c	C source code file
.c++	C++ source code file
.cab	Microsoft installation archive Cabinet file
.cas	Comma-delimited ASCII file
.cc	C++ source code file
.ccb	Visual Basic animated button configuration
.cel	Autodesk AnimatorLumena Graphics
.cfg	Configuration file
.cgi	Common Gateway Interface script
.cgm	Computer Graphics Metafile vector graphics
.chd	FontChameleon Font descriptor
.chk	ChkDsk recovered data
.cif	Caltech Intermediate Format graphics
.cif	Easy CD Creator CD image file
.class	Compiled Java class file
.cls	C++ class definition file
.cmf	Creative Music File FM-music file
.cnt	Helpfile contents
.col	Microsoft Multiplan spreadsheet
.contact	Windows Contacts contact entry
.cpi	Colorlab Processed Image bitmap graphics
.cpi	DOS Code Page Information file
.cpp	C++ source code file
.cps	Colored PostScript files
.crf	Microsoft MASMZortech C++ cross-reference
.cs	C# source code file
.csv	Comma Separated Value text file format (ASCII)
.ctx	Microsoft online guides Course TeXt file
.ctx	Pretty Good Privacy RSA System cipher text file
.cvp	WinFax cover page
.cvs	Canvas graphics
.dat	Datafile (generic)
.dbg	Microsoft C/C++ symbolic debugging information
.dcr	Shockwave file
.dcs	CYMK format bitmap graphics
.ddb	Bitmap graphics
.dev	Device driver (old)
.dib	Device-Independent Bitmap bitmap graphics
.dic	Lotus Notes/Domino dictionary file
.dip	Graphics
.diz	Description In Zip description file
.dlg	Microsoft Windows SDK dialog resource script file
.doc	Microsoft Word document
.dot	Word for Windows template
.drv	Device driver (old)
.dvr-ms	Windows Media Center recorded video file
.dxf	AutoCAD Drawing Interchange File format vector graphics
.emf	Enhanced Metafile graphics
.eml	Microsoft Outlook Express electronic mail
.eps	Adobe Illustrator Encapsulated PostScript vector graphics
.evt	Event log
.exe	Executable program
.f77	Fortran 77 source code file
.faq	Frequently Asked Questions text file
.fax	Incoming fax
.fd	Microsoft Fortran Declaration file
.ff	Agfa Compugraphics Outline font description
.ffl	Microsoft Fast Find file
.ffo	Microsoft Fast Find file
.ffx	Microsoft Fast Find file
.fhx	Macromedia FreeHand version x vector graphics
.fh4	Macromedia FreeHand 4.x vector graphics
.fi	Microsoft Fortran Interface file
.fif	Fractal Image Format file
.flc	Autodesk Animator animation
.fli	Autodesk Animator animation
.fm	FrameMaker document
.fm1	Lotus 1-2-3 release 2.x spreadsheet
.fm3	Lotus 1-2-3 release 3.x spreadsheet
.fmb	WordPerfect for Windows File Manager button bar
.fnt	Font file
.fon	Windows 3.x font library font file
.fot	Windows Font Installer installed TrueType font
.frf	FontMonger Font
.frm	Visual Basic form
.fts	Windows Help full-text search index file
.fxs	WinFax fax transmit format graphics
.gadget	Windows Gadget
.gcd	Graphics
.gwi	Groupwise file
.gz	GNU ZIP compressed file archive created by GZIP
.h	Header file (used with .c source code)
.h++	C++ header file
.hdf	Help Development Kit help file
.hgl	HP Graphics Language graphics
.hh	C++ header file
.hlp	Help information
.hpf	PageMaker HP LaserJet fonts
.hpj	Microsoft Help Compiler help project
.hqx	Compressed Macintosh file archive created by Binhex
.htm	HyperText Markup Language document
.html	HyperText Markup Language document
.htt	HyperText template
.hxx	C++ header file
.ical	iCalendar file
.icb	Bitmap graphics
.icn	Icon source code file
.ilk	Microsoft ILink incremental linker outline of program's format
.imp	Lotus Improv spreadsheet
.imz	Compressed floppy image
.inc	Include file (programming)
.inf	Information text file
.inf	Install script/Driver information
.ini	Initialization file
.ion	File description (e.g., descript.ion)
.iso	CD or DVD image file
.isr	Microsoft Streets & Trips route file
.jar	Java archive file
.jas	Graphics
.java	Java source code file
.jff	JPEG File Interchange Format bitmap graphics
.jpg	JPEG image file
.jsp	Java Server Page
.jtf	JPEG Tagged Interchange Format bitmap graphics
.kar	MIDI file with karaoke word track
.key	Keyboard macros
.lbm	DeluxePaint bitmap graphics
.ldb	Microsoft Access data
.lex	Lexicon
.lha	Compressed file archive created by LHA/LHARC
.lib	Library file (programming)
.lif	Compressed file archive
.lnk	Windows shortcut
.log	Logfile (text)
.lrf	Microsoft C/C++ Linker response file
.lwz	Microsoft Linguistically Enhanced Sound file
.lzh	Compressed file archive created by LHA/LHARC
.lzs	Compressed file archive created by LARC
.lzx	Compressed file archive
.m3u	Media playlist
.mak	Makefile
.mak	Visual Basic project file
.man	Command manual
.map	Color palette
.map	Linker map file
.mat	Matlab datafile
.mbx	Eudora mailbox
.mda	Microsoft Access data
.mdb	Microsoft Access database
.mdl	3D Design Plus model
.mdt	Microsoft ILink incremental linker data table
.me	ASCII text file (e.g., READ.me)
.mht	Microsoft MHTML document
.mic	Microsoft Image Composer file
.mif	FrameMaker Maker Interchange Format
.mim	MIME file (used for email attachments)
.mk	Makefile
.mke	Microsoft Windows SDK makefile
.mmf	Microsoft Mail mail message file
.mny	Microsoft Money Account book
.mov	QuickTime movie
.mp2	MPEG audio or video file
.mp3	MPEG Layer 3 audio file
.mp4	MPEG-4 movie
.mpc	Microsoft Project Calendar file
.mpe	MPEG movie clip
.mpd	Microsoft Project database file
.mpg	MPEG movie
.mpp	Microsoft Project project file
.mpv	Microsoft Project view file
.mrb	Microsoft C/C++ Multiple Resolution Bitmap graphics
.msc	Microsoft C makefile
.msi	Windows Installer file
.mso	Microsoft FrontPage file
.msp	Microsoft Paint bitmap graphics
.mst	Microsoft Windows SDK setup script
.msw	Microsoft Word text file
.mswmm	Windows Movie Maker project
.mxt	Microsoft C data
.nfo	Info file (ASCII)
.nlm	Netware Loadable Module
.nsf	Lotus Notes/Domino database
.nt	Windows NT Startup files
.ntf	Lotus Notes/Domino template file
.nws	Info text file
.nxt	NeXT format sound
.ofm	Adobe font
.oft	Microsoft Outlook Item template
.ogg	Ogg Vorbis music file
.old	Backup file (generic)
.one	Microsoft Office OneNote file
.ost	Microsoft Outlook Offline file
.out	Output file (ASCII)
.p65	Adobe PageMaker v6.5
.pab	Microsoft Outlook personal address book
.pak	Compressed file archive created by PAK; also a Quake game file
.pal	Color palette
.pas	Pascal source code file
.pb	WinFax Pro phonebook
.pbi	Microsoft Source Profiler profiler binary input
.pbm	Portable Bit Map graphics
.pbo	Microsoft Source Profiler profiler binary output
.pbt	Microsoft Source Profiler profiler binary table
.pcc	PC Paintbrush Cutout picture vector graphics
.pcd	Kodak PhotoCD graphics
.pcf	Microsoft Source Profiler profiler command file
.pch	Microsoft C/C++ precompiled header
.pcl	HP Printer Control Language HP-PCL graphics data
.pcx	PC Paintbrush bitmap graphics
.pda	Bitmap graphics
.pdb	Palm database
.pdd	Adobe PhotoDeluxe image
.pdf	Adobe Portable Document Format
.pfb	Type 1 font file
.pfm	Type 1 font metric file
.pgm	Portable Grayscale bitmap graphics
.pgp	Pretty Good Privacy RSA System Support file
.ph	Microsoft C/C++ Phrase-table
.ph	Perl header file
.pic	PC Paint bitmap graphics
.pka	Compressed file archive created by PKARC
.pkg	NeXT/Mac OS X Installer archive
.pl	Perl source code file
.pl1	3D Home Architect room plan
.pm3	PageMaker 3 document
.pm4	PageMaker 4 document
.pm5	PageMaker 5 document
.png	Portable Network Graphics bitmap
.pnm	Graphics file (Portable aNy Map)
.pov	Persistence Of Vision raytraced graphics image
.ppd	Acrobat PostScript Printer Description
.ppm	Portable Pixel Map graphics
.ppt	PowerPoint presentation
.pr2	Adobe Persuasion 2.x presentation
.pr3	Adobe Persuasion 3.x presentation
.prc	Palm resource file
.prj	Project
.ps	PostScript file
.psd	Photoshop image
.pst	Microsoft Outlook personal folder
.pt3	PageMaker 3 template
.pt4	PageMaker 4 template
.pub	Microsoft Publisher Page template
.pub	Pretty Good Privacy RSA System Public key ring file
.pwl	Password List
.py	Python script file
.pyc	Compiled Python script file
.qbw	QuickBooks for Windows spreadsheet
.qdat	QuickTime Installer cache
.qdb	Quicken datafile
.qdf	Quicken for Windows datafile
.qdt	Quicken datafile
.qfl	Quicken Family Lawyer file
.qfx	QuickLink fax
.qic	Backup set for Microsoft Backup
.qif	Quicken Interchange Format
.qlb	Microsoft C/C++ Quick library
.qlp	QuickLink Printer driver
.qt	QuickTime movie
.qxd	QuarkXPress Document
.qxl	QuarkXPress Element library
.r00, .r01	Compressed file archive created by RAR (supplemental to .rar)
.ra	RealMedia file
.ram	RealMedia shortcut
.rar	Compressed file archive created by RAR
.ras	Sun Rasterfile graphics
.rc	Microsoft C/C++, Borland C++ Resource script
.rcg	Netscape newsgroup file
.rdp	Remote Desktop Connection Profile
.ref	Cross-reference
.res	Microsoft C/C++, Borland C++ Compiled resource
.rib	3DReality Graphics in Renderman format
.rif	Fractal Design Painter Riff bitmap graphics
.rl4	Bitmap graphics
.rl8	Bitmap graphics
.rlc	Graphics 1-bit/pixel scanner output
.rtf	Windows Word Rich Text Format text file (Word)
.rtf	Windows Help file script
.rvp	Microsoft Scan Configuration file
.sav	Configuration file
.sav	Backup file
.sbi	Creative Labs Sound Blaster Instrument file
.sco	High score
.sdf	System Data Format (ASCII)
.sea	Self-Extracting compressed Macintosh file Archive
.search-ms	Windows Vista saved search folder
.sec	Pretty Good Privacy RSA System Secret key ring file
.sfi	HP LaserJet landscape printer font
.sif	Windows NT Setup Setup Installation Files info
.sit	Compressed Macintosh archive created by STUFFIT
.sng	MIDI sound Song
.spc	Microsoft Multiplan Program
.srp	QuickLink Script
.ssm	RealPlayer Standard Streaming Metafile
.sts	Microsoft C/C++ Project status info
.swf	ShockWave Flash object
.sys	Windows or DOS System filedevice driver or hardware configuration info
.tar	Compressed file archive created by TAR
.taz	Compressed file archive created by TAR and COMPRESS (equiv. to .tar.Z)
.tga	Truevision Targa bitmap graphics
.tgz	Compressed file archive created by TAR and GNUzip (equiv. to .tar.gz)
.thm	Microsoft Clipart Gallery database
.tif	Tagged Image File Format bitmap graphics
.tis	MahJongg 3.0 Tile set
.tlb	Visual C++ Type library
.tmp	Temporary file
.toc	Eudora Table Of Contents
.torrent	BitTorrent
.tpz	Compressed file archive created by TAR and GNUzip (equiv. to .tar.gz)
.ttf	TrueType Font file
.txt	Text file
.tym	PageMaker Time Stamp
.tz	Compressed file archive created by TAR and COMPRESS (equiv. to .tar.Z)
.uhs	Universal Hint System
.uu	Compressed ASCII file archive created by UUEncode/UUDecode
.uue	Compressed ASCII file archive created by UUEncode/UUDecode
.vbs	Visual Basic Script file
.vbx	Visual Basic Visual Basic eXtension (custom control)
.vcf	VCard file
.vcw	Microsoft Visual C++ Visual workbench information
.vda	Bitmap graphics
.vmc	Acrobat reader Virtual Memory Configuration
.vnc	VNC connection profile
.vob	DVD video movie file
.voc	Creative Voice file Digitized samples
.vds	Visio drawing file
.vue	3D Studio animation
.vxd	Virtual device driver
.wab	Outlook (Windows Address Book) file
.wad	Doom game file
.wav	Waveform audio file
.wb1	Quattro Pro Notebook
.wb2	Quattro Pro Spreadsheet
.wba	Winace ZIP file
.wba	WindowBlinds Compressed Skin for Windows XP
.wbk	WordPerfect for Windows document/workbook
.wcm	Microsoft Works Data transmission file
.wdb	Microsoft Works Database
.wdl	Windows XP Watchdog Log file
.wfx	WinFax datafile
.wiz	Microsoft Publisher Page wizard
.wk1	Lotus 1-2-3 version 2.xSymphony 1.1+ spreadsheet
.wk3	Lotus 1-2-3 version 3.x spreadsheet
.wk4	Lotus 1-2-3 version 3.4 spreadsheet
.wkb	WordPerfect for Windows document
.wkq	Quattro spreadsheet
.wks	Lotus 1-2-3 version 1ASymphony 1.0Microsoft Works spreadsheet
.wma	Microsoft Windows Media Active Streaming file
.wmf	Windows MetaFile vector graphics
.wmv	Microsoft Active Streaming file
.wn	NeXT WriteNow Text
.wp	WordPerfect 4.2 text file
.wp5	WordPerfect 5.x document
.wpm	WordPerfect macros
.wps	Microsoft Works text document
.wq1	Quattro Pro spreadsheet
.wri	Windows Write text file
.wrl	VRML file
.wrml	VRML file
.wsz	WinAmp Skin ZIP file
.xla	Microsoft Excel Add-in macro sheet
.xlb	Microsoft Excel data
.xlc	Microsoft Excel Chart document
.xll	Microsoft Excel Excel Dynamic Link Library
.xlm	MS Excel Macro sheet
.xlr	Microsoft Works file
.xls	Microsoft Excel worksheet
.xlt	Microsoft Excel template
.xlw	Microsoft Excel workbook
.xmi	Compressed extended MIDI music
.xml	XML document
.xnk	Microsoft Exchange Shortcut
.xps	XPS Document (Paper Specification)
.xsl	XSL stylesheet
.xwk	Crosstalk keyboard mapping
.xwp	Crosstalk session
.z	Compressed file archive created by COMPRESS
.z3	Infocom game module
.z5	Inform game module
.zip	Compressed ZIP file archive
.zoo	Compressed file archive created by ZOO