| Extension | File Type | Files scanned | Contributor |
| A2B | DigitalPhono A2B Player Playlist | 4 | |
| A3D | Eovia Amapi 3D model | 5 | |
| A3W | Unpackaged Authorware 3 for Windows file | 6 | |
| A4P | Authorware file (w/o runtime) | 9 | |
| A4R | Adobe Authorware Package | 3 | |
| A78 | Atari 7800 ROM | 10 | |
| AA | Audible Audio | 11 | |
| AAC | Astrid/Quartex AAC encoded audio | 6 | |
| AAC | MPEG-2 LC-AAC Audio | 6 | |
| AAC | MPEG-4 LC-AAC Audio | 3 | |
| AAM | Authorware Shocked File (Map) | 31 | |
| AAS/AOS | Archos signed / encrypted data | 6 | |
| AB1/FSA | ABIF - Applied Biosystems Inc. Format | 21 | |
| ABA | Palm Address Book | 5 | |
| ABD | The Bat! Address Book | 17 | |
| ABF | Altair Binary Format | 17 | |
| ABK | 'Need for Speed: Underground' audio file | 79 | Alvin Abdagic |
| ABK | AMOS Music Bank | 20 | |
| ABM | Audition music | 2 | |
| ABR | Adobe PhotoShop Brush | 15 | |
| ABS | Absolute Database file | 11 | |
| ABW | AbiWord document | 30 | |
| ABY | AOL Address Book | 14 | |
| AC | AC3D geometry/model | 22 | |
| AC1D | AC1D-DC1A Packer | 7 | |
| ACB | Adobe Photoshop Color Book | 17 | |
| ACCDB | Microsoft Access 2007 Database | 5 | |
| ACD | ALAN game | 11 | |
| ACD | Sonic Foundry Acid music | 6 | |
| ACE | ACE compressed archive | 14 | |
| ACE | Jupiter Ace snapshot | 6 | |
| ACF | DB/TextWorks Database Access Control | 6 | |
| ACF | Microsoft Agent Character | 4 | |
| ACF | X-Plane Aircraft | 25 | |
| ACM | Windows Audio Compression Manager driver | 54 | |
| ACP | ArCon project | 4 | |
| ACP/PCAP | TCPDUMP's style capture | 20 | |
| ACR | American College of Radiology file | 6 | |
| ACS | Microsoft Agent Character | 14 | |
| ACT | ADPCM (?) compressed file recorded by some MP3 Players/Voice recorders | 6 | THE LoW |
| AC_ | CaseWare 2005 Compressed file | 474 | Jim Grusendorf |
| AD | Mac AppleDouble encoded | 5 | |
| ADA | Advanced Digital Audio compressed audio | 21 | |
| ADB | CorelCENTRAL Address Book | 2 | |
| ADF | Amiga Disk image File (generic) | 12 | Wayne Hardman |
| ADF | Antenna Data File | 75 | |
| ADI/ADIF | Amateur Data Interchange Format | 13 | |
| ADL | openEHR Archetype Definition Language | 6 | |
| ADM | Addict compiled dictionary | 14 | |
| ADM | Windows Policy Administrative Template | 12 | |
| ADM | Windows Policy Administrative Template (Unicode) | 7 | |
| ADM | Windows Policy Administrative Template (with rem) | 7 | |
| ADP | Microsoft Access Project | 26 | |
| ADR | Opera Hotlist (v2.0) / bookmark | 4 | |
| ADT | Advantage Data Server table | 4 | |
| ADT | Casio Pocket Viewer Add-in Data file | 3 | |
| ADU | Addict User Dictionary | 2 | |
| ADX | Lotus Approach database index | 8 | |
| ADX | Sega Dreamcast audio | 13 | |
| AEF | CA Visual Object Application Export File | 21 | |
| AEH | iPer Advanced Embedded Hypertext | 24 | |
| AEP | ArcExplorer Project | 14 | |
| AFF | AGEMA File Format | 2 | |
| AFF | Advanced Forensics Format disk image | 4 | |
| AFF | Affix file | 7 | |
| AFL | X-Plane Airfoils | 52 | |
| AFM | Outline Font Metric | 8 | |
| AG | Applixware Graphic | 9 | |
| AGN | Psion Serie 3 Agenda | 6 | |
| AGR | Grace project file | 10 | |
| AHX | THX Tracker music | 19 | |
| AI | Adobe Illustrator graphics | 67 | |
| AI | Ai Archivator compressed archive | 12 | |
| AIC | Advanced Image Coding bitmap | 6 | |
| AIF/AIFF | AIFF Audio Interchange File Format | 21 | James Heinrich |
| AIFC | AIFF-C (Audio Interchange File Format Compressed) | 3 | |
| AIG | Abracadata drawing | 2 | |
| AIML | Artificial Intelligence Markup Language | 93 | |
| AIN | AIN compressed archive | 3 | |
| AIP | Advanced Installer Project | 5 | Paul Beesley |
| AIR | Adobe Apollo Rich Internet Application (obsolete) | 22 | |
| AIR | Adobe Integrated Runtime | 13 | |
| AIRPORTS | RealFlight Radio Control Flying Site - Airport | 2 | |
| AJP | Anfy Applet Generator Saved file | 20 | |
| AK | TracerCAD File (generic) | 2 | |
| AKM | Aksharamala Keymap Binary | 87 | Srinivas Annam |
| AKT | AKT compressed archive | 3 | |
| ALB | VCOM Web Easy album | 19 | |
| ALBM | HP Photosmart Photo Printing Album | 36 | |
| ALC/VLC | AcuCorp AcuCOBOL license | 7 | |
| ALM | Aley's Module v1.0 | 4 | |
| ALM | Aley's Module v1.1-1.2 | 3 | |
| ALS | MPEG-4 ALS (Audio Lossless coding Standard) | 10 | |
| ALX | BlackBerry Application Loader | 27 | |
| ALZ | ALZip compressed archive | 8 | |
| AMC | A.M.Composer 1.2 Music | 6 | |
| AMD | Amusic tracker (packed) song/module | 50 | |
| AMF/AMFF | Amiga Meta File Format | 2 | |
| AML | Morpheus layout - project | 2 | |
| AMR | AMR (Adaptive Multi Rate) encoded audio | 14 | |
| AMS | Velvet Studio Advanced Module System song/module | 2 | |
| AMT | ArtMoney Table File | 444 | .Cryorb |
| AMV | MTV Movie | 9 | |
| AMXX | AMX Mod X plugin | 10 | |
| AN8 | Anim8or project | 4 | |
| ANA | Analysis for Windows structure | 4 | |
| ANB | Enter a useful file type description | 2 | |
| ANB | Project Dogwaffle Animated Brush | 9 | |
| ANI | Atari NEOchrome animation | 4 | |
| ANI | Windows Animated Cursor | 34 | |
| ANIM | IFF ANIM (Amiga delta/RLE encoded bitmap animation) | 19 | Wayne Hardman |
| ANM | DeluxePaint Animation | 10 | |
| ANS | ANSYS model data | 6 | |
| ANS/ASC | ANSI ISO 6429 ASCII file | 15 | |
| AOM | Adobe Download Manager | 12 | |
| AOP | AOP data | 2 | |
| AOS | AOS File Format | 6 | |
| AP | ArmPack Archive File | 11 | .Cryorb |
| APC | Cryo Interactive APC audio | 7 | |
| APC | a-Pac compressed audio | 29 | |
| APE | Monkey's Audio | 51 | |
| APF | MightyFax | 21 | |
| API | Adobe Acrobat Reader Plugin | 12 | |
| APK | Android Package | 5 | |
| APL | ACDSee plugin | 36 | fenixproductions |
| APL | Monkey's Audio Image Link file | 4 | |
| APM | Aldus Placeable Metafile | 2 | |
| APN | APN Wallpaper | 25 | |
| APP | Generated application MS Visual FoxPro 7 | 21 | Nicola Marangon |
| APP | OrbWorks PocketC CE Application | 15 | |
| APP | Psion Oval Application | 13 | |
| APP | Symbian Application | 5 | |
| APP | Timex Datalink Wristapp file | 4 | |
| APPLICATION | ClickOnce Deployment Manifest | 4 | |
| APR | ArcView Project | 32 | |
| APR | Lotus Approach (generic) | 13 | |
| APR | Lotus Approach 9.5 | 11 | Vincent |
| APT | Adaptive Prediction Tree (APT) encoded bitmap | 9 | |
| APV | API Viewer Database | 3 | voodooattack |
| APW | Any Password data | 2 | |
| AQ1 | AptiQuiz quiz data | 2 | |
| AR | AIX Small indexed archive (AIX prior to v4.3) | 7 | |
| AR | Midtown Madness 2 car data | 8 | |
| ARC | EZBIND archive | 3 | |
| ARC | FreeArc compressed archive | 7 | |
| ARC | RARC compressed archive | 4 | |
| ARC/SZS | Yaz0 compressed data | 4 | |
| ARCH00 | F.E.A.R. game archive | 16 | |
| ARE | Infinity Engine area description (v1.0) | 2 | |
| ARF | Active Tutor data | 6 | |
| ARF/FTS | Flexible Image Transport System bitmap | 21 | |
| ARGO | ArgoUML project | 2 | |
| ARJ | ARJ compressed archive | 45 | |
| ARK | QuArk compressed archive | 4 | |
| ARN | CD Autorun Creator package | 2 | |
| ARP | Audition Play Data | 5 | |
| ART | AOL ART (Johnson-Grace compressed) bitmap | 9 | |
| ART | Bernina Artista | 30 | FILExt |
| ART | Gerber artwork | 6 | |
| ARW | Sony digital camera RAW image | 11 | |
| ARX | ARX compressed archive | 6 | |
| AS | Applix spreadsheet | 10 | |
| AS | Mac AppleSingle encoded | 9 | |
| ASD | ASD Archiever compressed archive | 4 | |
| ASE | 3D Studio Max ASCII Export file | 14 | |
| ASF | FIFA 2004 audio file | 337 | Alvin Abdagic |
| ASH | ASH compressed data | 17 | Label |
| ASK | askSam database | 5 | |
| ASM | Solid Edge Assembly Document | 123 | |
| ASM | freeCAD assembly | 15 | |
| ASS | SubStation Alpha Subtitle (Unicode) | 31 | |
| ASS/SSA | SubStation Alpha Subtitle | 29 | |
| AST | 'Need for Speed: Underground' soundtrack | 4 | |
| AST | AST Audio Stream | 5 | |
| AST | Actionamics Sound Tool | 3 | |
| ASWCS | avast! antivirus skin | 7 | |
| ASX | Advanced Stream Redirector | 13 | |
| ATA | Antenna project | 27 | |
| ATH | Athena document (v1.x) | 25 | |
| ATH | Athena document (v2.x) | 3 | |
| ATM | TerraGen Light and Atmosphere | 20 | Chris Malady |
| ATM | Vue D'Esprit 4 Atmosphere Preset | 138 | Alex Paven |
| ATN | Photoshop Action | 30 | |
| ATP | ATRAC encoded audio | 7 | |
| ATR | Atari ATR Disk Image | 18 | |
| ATTR | iPhoto image data | 87 | |
| AU | Audacity audio block | 246 | |
| AU | NeXT/Sun uLaw/AUdio format | 11 | James Heinrich |
| AUF | Audacity Block File | 2 | |
| AUM | Adobe Update Manager data | 6 | |
| AUM | Adobe Update Manager data (UTF-8) | 4 | |
| AUP | Audacity project | 2 | |
| AUR | AutoREALM Map | 6 | |
| AUS | AutoREALM Symbols | 5 | |
| AVB | Avid Editor Bin file | 64 | Daniel |
| AVB | Microsoft Chat Character | 30 | |
| AVC | Kaspersky Anti-virus data base | 139 | kif aka AC |
| AVI | AVI Audio Video Interleaved | 93 | |
| AVP | Avira AntiVir Virus scanner Parameters | 14 | |
| AVR | Audio Visual Research sound | 2 | |
| AVS | Winamp Advanced Visualization Studio File | 112 | .Cryorb |
| AW | Microsoft Answer Wizard | 44 | |
| AWB | Adaptive Multi-Rate Wideband ACELP codec | 2 | |
| AWD | Artweaver Document | 3 | |
| AWD | Microsoft At Work Fax document | 13 | |
| AWL | AWL programming language (Var. 1) | 10 | |
| AWL | AWL programming language (Var. 2) | 10 | |
| AWLIVE | Active WebCam live capture | 4 | |
| AWM | AllWebMenus project (v2.xx) | 6 | |
| AWM | AllWebMenus project (v3.xx) | 6 | |
| AWM | AllWebMenus project (v4.xx) | 32 | |
| AWS | Ability Office Spreadsheet | 14 | |
| AX | DirectShow filter | 78 | |
| AXE | AutoRoute Export file | 13 | |
| AXT | ZenWorks snAPPshot ASCII Application Object Template | 7 | |
| AXX | AxCrypt encrypted | 6 | |
| AY | AY Chip Sound / Music | 730 | |
| AYM | Z80 music code with AY music | 27 | |
| AZA | QazaR compressed file | 3 | |
| AZX | ZX Audio | 2 | |
| AZZ | AZZ Cardfile card | 10 | |
