A

File extensions starting with the letter A...

  .A    UNIX Library  [UNIX]
        ADA Program
  .A01  ARJ Multi-volume Compressed Archive (can be 01 to 99)
  .A11  Graphic
  .A3K  Yamaha A3000 Sampler File
  .A3L  Authorware 3.x Library
  .A3M  Unpackaged Authorware MacIntosh File
  .A3W  Unpackaged Authorware Windows File
  .A4L  Authorware 4.x Library
  .A4M  Unpackaged Authorware MacIntosh File
  .A4P  Authorware File Without Runtime
  .A4W  Unpackaged Authorware Windows File
  .A5L  Authorware 5.x Library
  .A5W  Unpackaged Authorware Windows File
  .A86  A86 Assembler Program File
  .A_T  A-Train  
  .AA   Audio Book File
  .AAM  Authorware Shocked File
  .AAS  Authorware Shocked Packet
  .AB   Applix Builder File
  .AB6  AB Stat Data
  .AB8  AB Stat Data
  .AB\$  AutoCAD Spooled Plot File
  .ABC  Flowchart
  .ABD  AmBiz Bonus Calculator Data File
  .ABF  Adobe Binary Screen Font
  .ABK  Corel Draw AutoBackup
        Any Automatic Backup
  .ABM  HitPlayer Audio Album File
        Album File (various)
  .ABO  Applix Builder Turbo File
  .ABR  Photoshop Brush
  .ABS  Abstracts
        MPEG Audio Sound File  [MPEG]
        PC GNU Compiler Output
        Abscissa Data File
  .ABW  AbiWord Document File
  .ACA  MS Agent Character File
        Project Manager Workbench File
  .ACB  ACBM Graphic Image
        Archived Data File
  .ACC  DR-DOS Viewmax File
  .ACD  Chromeleon Channel Raw Data
        Sonic Foundry Acid Music File
        MS Agent Character Definiton File
  .ACE  The Ace Archiver Compressed File
  .ACF  MS Agent Character File
        Photoshop Custom Filter
  .ACG  MS Agent Preview File
  .ACH  Rockwell Software Logix 5 File
  .ACI  ACI Development Appraisal
  .ACL  Corel Draw 6 Keyboard Accelerator
  .ACM  Audio Compression Manager Driver (Windows)
        Photoshop Command Button
        Windows System File
        ACBM Image File
        Interplay Compressed Sound File
  .ACO  Photoshop Color Swatch File
  .ACP  MS Office Assistant Preview File
        File Used by Adobe Acrobat Paper Capture
  .ACR  American College of Radiology File
  .ACS  MS Agent Character File
  .ACT  MS Office Actor Program File
        FoxPro Documenting Wizard Action Diagram
        Photoshop Color Table
  .ACV  OS/2 Audio Drivers
        Photoshop Saved Curve  Also see
  .AD   AfterDark Screen Saver
  .AD2  2-bit Compressed Voice File
  .AD3  3-bit Compressed Voice File
  .ADA  ADA Program File
  .ADB  ADA Package Body
        HP Organizer Appointment Database
  .ADC  Chromeleon Demo Data File
        Scanstudio 16-color Bitmap Graphic File
        Lingvo Dictionary Text File
  .ADD  OS/2 Adapter Device Driver
        Adobe Pagemaker File
  .ADE  MS Access Project Extension
        ADC Audio File
  .ADF  Adapter Description File
        Admin Config File
        Amiga Disk File (Uncompressed 901120 byte DD Diskimage)
  .ADI  AutoCAD Plotter File
  .ADL  QEMM MCA Adapter Description Library  [MCA]
  .ADM  After Dark Screen Saver Module
        Windows NT Policy Template
        Addict Compiled Dictionary
  .ADN  1-2-3 Add In Utility
        MS Access Blank Project Template
  .ADO  Photoshop Duotone Options
  .ADP  FaxWorks Modem Setup File
        Astound Dynamite File
        MS Access Project
        AOLserver Dynamic Page File  [AOL]
  .ADR  After Dark Random Screen Saver Module
        Smart Address Address Book
  .ADS  ADA Package Specification
  .ADT  HP NewWave Card Application Data File
        Lingvo Dictionary File
        AdTech Fax File
  .ADV  GUS Virtual Device Driver
  .ADX  Lotus Approach Index File
        Archetype Designer Document
        Dynazip Active Delivery Script
  .ADZ  GZ-Packed Amiga Disk File (see ADF)
  .AE   SoftQuad Author/Editor File
  .AEH  iPer Advanced Embedded Hypertext
  .AEP  ArcExplorer Project File
  .AEU  MS AutoRoute Express Europe Route
  .AEX  PGP Armored Extracted Public Encryption Key  [PGP]
  .AF2  ABC Flowchart (Now Micrografx FlowCharter)
  .AF3  ABC Flowchart (Now Micrografx FlowCharter)
  .AFC  Apple Sound File
  .AFI  Truevision Bitmap Graphic
  .AFL  Lotus Font
  .AFM  Outline Font Metric
        HP NewWave Cardfile Application
  .AFP  Flowchart Symbol Palette  
  .AFS  Filter Factory Photoshop Filter  [Added]
  .AFT  Flowchart Template
  .AFW  Flowchart Work Area
  .AG   Applix Graphic
  .AG4  Access G4 File
  .AGP  Aspen Graphics Pages
  .AGW  Aspen Graphics Windows
  .AHS  Photoshop Halftone Screens
  .AI   Adobe Illustrator Vector Graphic
        Corel Trace Drawing
        Progress Database After Image File
  .AIF  Knowledgeware Setup Information
        Audio Interchange File  [Viewer]  
  .AIM  AOL Instant Messenger File  [AOL]
  .AIML  Artificial Intelligence Markup Language
  .AIN  AIN Compressed Archive
  .AIO  APL File Transfer Format
  .AIP  Audiosoft Parameter File
  .AIR  Align It! Resource File
  .AIS  Array of Intensity Samples (Graphic)  
        Velvet Studio Instruments
        ACDSee Image Sequence File
  .AIX  HP NewWave Cardfile Application Data
  .AKF  Acrobat Key File
  .AKW  RoboHELP Help Project Index File
  .ALB  JASC Image Commander Album
        Steinberg Cubase or VST Backup Song File
  .ALC  Norton Internet Security Ad Server File
  .ALI  SAP Proprietary Format Document File
  .ALL  Arts & Letters Symbols and Characters
        WordPerfect Printer Info
        Steinberg Cubase or VST Song File
  .ALS  Alias Image
  .ALT  WordPerfect Menu File
  .ALV  Photoshop Levels
  .AM   Applix SHELF Macro
  .AMF  Advanced Module Format Music File
        DSMIA/Asylum Module Music  
  .AMG  AMGC Compressed Archive (alternate site)
        AMG ACTOR System Image
  .AMI  Cocreate SolidDesigner Annotation File
  .AMP  Photoshop Arbitrary Map Settings
  .AMS  Extreme's Tracker Module Format
        Photoshop Monitor Setup
        Velvet Studio Module
  .AN   Groundworks Text File 
  .ANC  Canon Computer Pattern Maker File
  .ANI  Animated Cursor  [Viewer]
  .ANL  Project Analyzer Saved Analysis
  .ANM  DeluxPaint Animation
  .ANN  Help Annotation
  .ANS  ANSI Graphic  [ANSI]
        MS Word Text and Layout
  .ANT  SimAnt for Windows Saved Game File
  .AOF  Acorn Object Format (used for data storage)
  .AOS  Nokia Add-on Software
  .AOT  ZenWorks Application Binary Object Template File
  .AP   Applix Presents File
        WHAP-Compressed Amiga Archive
  .APA  AlfaPad Organizer File
  .APC  Lotus Printer Driver Characters
        Centura Team Developer Compiled Application File
  .APD  Lotus Printer Driver
        Centura Team Developer Dynamic Application Library File
  .APF  Lotus Printer Driver Fonts
        Acrobat Profile File
        Homesite Project File
  .API  Lotus Printer Driver Info
        Photoshop Ink Colors Setup
        Application Program Interface
  .APK  GameSpy Arcade Service
  .APL  Centura Team Developer Application Library File
        APL Workspace File
  .APP  R:Base, Symphony, DR-DOS, FoxPro (or other) Application
        Centura Team Developer Normal Mode Application File
  .APR  Lotus Approach 97 File
        ArcView Project File
        Employee Appraiser Performance Review File
  .APS  MS Visual C++ File
        Advanced Patching Systems with Error Checking
  .APT  Centura Team Developer Text Mode Application File
        Lotus Approach Data View File
  .APX  Lotus Approach Paradox-specific Information File
        Borland C++ Appexpert Database
  .AQ   Applix Data
  .ARC  Archive File
        Compressed File
  .ARF  Automatic Response File
  .ARI  Aristotle Audio File
        Compressed Archive
  .ARJ  Compressed Archive
  .ARK  Compressed Archive
  .ARL  AOL Organizer File  [AOL]
  .ARM  Armadillo Software Protection System
  .ARR  Atari Cubase Arrangement
  .ART  Clip Art File
        Xara Studio Drawing
        Canon Crayola Art File
        Another Ray Tracer Format
        AOL Johnson-Grace Compressed File  [AOL]
        First Publisher Raster Graphic
  .ARV  Arsiv File
  .ARX  Compressed Archive
  .AS   Applix Spreadsheet
  .ASA  MS Visual InterDev File
        Active Server Document
  .ASC  ASCII Text File  [ASCII]
        PGP Armored Encrypted File  [PGP]
  .ASD  MS Word Automatic Backup
        Lotus Screen Driver
        MS Advanced Streaming Format Description File  
  .ASE  Velvet Studio Sample
  .ASF  MS Active Streaming (Media) File
        Statgraphics Data
        Lotus Screen Font
        APL*Plus/PC APL Shared File
        Electronic Arts Music File
  .ASH  TASM Assembler Header
  .ASI  Borland Assembler Include
  .ASK  askSam Database
  .ASM  Assembler Source Language (various)
  .ASMX  ASP.NET Webservices Source File
  .ASO  Assembler Object
        Astound Dynamite Objects
  .ASP  Active Server Page
        Procomm Plus ASPECT Program
        Astound Presentation File
        Photoshop Photo File Index
        Photoshop Separation Setup
  .ASPX  ASP.NET Source File
  .ASR  Ms Automap Route
        Photoshop Scratch Area
  .AST  Astound Multimedia File
        Photoshop Separation Tables
        Claris Works Assistant File
  .ASV  DataCAD Autosave File
        Photoshop Selective Color
  .ASX  MS Windows Media Active Stream Redirector File
        Cheyenne Backup Script
        Video File
  .AT2  Aldus Persuasion 2.0 Auto Template
  .ATF  Photoshop Transfer Function
  .ATM  Adobe Type Manager Data File
  .ATR  Lightscape Material Library
  .ATT  AT&T Group 4 Bitmap (fax)
  .ATW  AnyTime Deluxe PIM File  [PIM]
  .AU   Music File (various)  [Viewer]
  .AUD  Audio File used by Westwood Studios for various games
  .AUX  TeX/LaTeX Auxilliary Reference File
        ChiWriter Auxilliary Dictionary File
  .AV   Final Draft AV Document File
  .AVA  Avagio Publication
  .AVB  Inoculan Anti-Virus Virus Infected File
        Microsoft Chat Character File
  .AVI  Audio Video Interleave File  [Viewer]
  .AVR  Audio Visual Research Sound File
  .AVS  Animation File
        Application Visualization System Format
        Stardent AVS-X Image
        Winamp Advanced Visualization Studio File
  .AVX  ArcView File
  .AW   HP AdvanceWrite Text File
        Applix Word File
  .AWB  Lavasoft Ad-aware Backup File
  .AWD  Faxviewer Document
  .AWK  AWK Script
  .AWM  Animation Works Movie
  .AWR  Telsis Digital Audio File
  .AWS  StatGraphics Data File
  .AXG  MS Autoroute Trip File
  .AXL  ArcIMS XML Project File  [XML]
  .AXR  Telsis Digital Audio File
  .AXT  ASCII Application Object Template 
        Photoshop Replace Color/Color Range