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File Types

This page houses a computer file extension library with a brief explanation. A file extension is simply the last characters after the stop (period) in the name of a file. Files with a shared common name extension (.doc, .html and so on) are of the same type.

File (Suffix) Characteristics
.aam media file Macromedia (Now Adobe) Shockwave.
.arc archive file
Open with PKZip or WinZip.
.asp web page Active server page – used to code web pages that connect to databases.
.au audio Sound file – open with player – used on older web pages.
.avi video clip Audio/Video Interleaved – movie clip – open with mplayer, or IE – see also .vlc
.bak backup file Used by many applications – often created automatically.
.bat application DOS batch file – run by double-clicking in early Windows – edit with Notepad.
.bmp graphic file Microsoft bitmap – open in MS Paint or graphics program.
.cab archive Microsoft installation achive (cabinet file) – similar to .zip archive.
.cfg Configuration file.
.cgi Common Gateway Interface – used to exchange information with a server.
.chk Data recovered after running Checkdisk.
.css style sheet Plain text file containing web page style preferences.
.csv data Comma Separated Value file – a way of presenting tabular data in a text file – usually viewed in MS Excel.
.dat data file Used by several applications. Not to be opened directly.
.dcr media file Macromedia (Now Adobe) Shockwave movie.
.dir media file Macromedia (Now Adobe) Director file – provides animation and interactivity.
.dll dynamic link library Software used by Windows to provide services to applications.
.doc document Microsoft Word file.
.docx document Microsoft Word 7, 10 file.
.dot template Microsoft Word template.
.dotx template Microsoft Word 7 template.
.drv device driver Used to control hardware – (old).
.dtd text Document type definition.
.exe application Self-extracting or executable file – run by double-clicking.
.faq data file Frequently Asked Questions – almost always a text file.
.fla media Macromedia (Now Adobe) Flash animation file – requires Shockwave.
.fnt Font file.
.ftl web page Family Tree Legends Document.
.gif image Graphic in GIF format – open in web browser or graphics program.
.gz application Compressed archive file created by Gzip in the UNIX operating system.
.htm text file Hypertext document (same as .html). Open in a web browser – edit in any word-processor or text editor.
.ico Windows icon Open with an icon editor.
.ini Initialisation file.
.jar Java Java compressed archive file.
.jav Java Cross platform programming language used to create complex interactive forms and special effects.
.jpg image Graphic in JPEG format (Joint Photographic Experts Group) View with web browser or image editing program.
.js JavaScript Part of web page used to create interactive effects such as mouse roll-overs and pop-up boxes.
.jso Java server page.
.kbd data file Keyboard layout data.
.log data file Created by many applications – usually a text file – edit in any text editor.
.mht single file web page Web page dowload file.
.mid audio Audio file in MIDI format.
.mov video QuickTime movie – or view using IE.
.mp3 audio Audio file in MP3 format – CD-quality sound, with 10x compression.
.mpg movie Video movie in MPEG format (Motion Picture Experts Group).
.old Backup file (generic).
.pdf application Portable Document Format – requires Adobe Acrobat Reader.
.pl application Perl source file – text file, editable in any text editor.
.png image Graphic in Portable Network Graphics format – can work on all platforms.
.ppt application Microsoft PowerPoint file – used for creating slides and overhead presentations.
.pptx application Microsoft PowerPoint 7 file – used for creating slides and overhead presentations.
.pub Microsoft Publisher page template file.
.ram audio Real Audio file – open in browser with RealAudio plug-in.
.rtf application Rich Text Format - word-processor file with formatting codes.
.scr screen saver  
.sig signature Appended to outgoing email messages – editable in text editor.
.swf media Macromedia (Now Adobe) Shockwave Flash animation movie.
.sys DOS system file – device driver or hardware configuration info.
.tar application File archive created in the Unix operating system.
.tif image Tagged Image File format – graphic file – editable in graphics program.
.tmp Temporary file – used by many programs.
.ttf font True Type Font file – view with fontview.
.txt text Contains only ASCII code – also called 'text file' – editable in any text editor.
.vlc video clip VideoLAN Client – movie clip – open with mplayer, or IE – see also .avi
.wav audio Sound file in Waveform format.
.wsz graphics Winamp skin – visual interface for audio control board.
.xls application Microsoft Excel worksheet file.
.xlsx application Microsoft Excel 7 worksheet file.
.xml web page Extensible markup language – a plain text file for web pages.
.zip application Compressed file – open with WinZip or PKZip.