| .A52 | Atari Corporation | Arquivos de jogos | Atari 5200 ROM | MESS | Open Source |
| .AAO | U.S Army | Arquivos de jogos | America's Army Map File | America's Army | U.S Army |
| .AAS | Adobe Systems Incorporated | Arquivos de jogos | Adobe Authorware Shocked Packet File | Adobe Authorware | Adobe Systems Incorporated |
| .ABG | Electronic Arts | Arquivos de jogos | FIFA World Cup Game Data File | FIFA World Cup | Electronic Arts |
| .ABK | Corel | Arquivos de jogos | Automatic Backup File | Ability Office | Ability Plus Software |
| .ABL | Ubisoft Blue Byte | Arquivos de jogos | ANNO 2070 Scenario Data | ANNO 2070 | Ubisoft Blue Byte |
| .ABM | Unknown Developer | Arquivos de jogos | Music Album | Redbana Audition | Redbana |
| .ABO | Pierre Chambart, Jean-Christophe FILLIATRE and Sylvain Le Gall | Arquivos de jogos | Applix Builder File | Camomile (Library File) | Pierre Chambart, Jean-Christophe FILLIATRE and Sylvain Le Gall |
| .ABZ | Playlogic | Arquivos de jogos | Alpha Black Zero Game File | Alpha Black Zero | Playlogic |
| .ACD | Sony Creative Software | Arquivos de jogos | ACID Project File | ACID XPress | Sony |
| .ACF | Valve | Arquivos de jogos | Steam Application Cache File | Valve Steam | Valve |
| .ACG | Bolide Software | Arquivos de jogos | Audio Comparer Group File | Audio Comparer | Bolide Software |
| .ACX | Atari Corporation | Arquivos de jogos | Atari ST Program | Gemulator | Open Source |
| .ADM | Microsoft Corporation | Arquivos de jogos | Administrative Template File | Microsoft Group Policy Object Editor | Microsoft Corporation |
| .ADT | Swiftpage, Inc. | Arquivos de jogos | ACT! Document Template | Swiftpage Act | Swiftpage, Inc. |
| .AGE OF EMPIRES / AGE OF MYTHOLOGY GAME FILE | Microsoft Corporation | Arquivos de jogos | Age Of Empires/Age Of Mythology Game File | Dragon UnPACKer | Open Source |
| .AGE3REC | Microsoft Corporation | Arquivos de jogos | Age Of Empires 3 Recording | Age of Empires III | Ensemble Studios |
| .AGE3SCN | Microsoft Corporation | Arquivos de jogos | Age Of Empires 3 Scenario File | Microsoft Age of Empires | Ensemble Studios |
| .AGX | Open Source | Arquivos de jogos | AGT Game File | AGiliTy | Open Source |
| .AHF | Anadigm | Arquivos de jogos | AnadigmDesigner ASCII Code | Anadigm Designer 2 | Anadigm |
| .AI | Adobe Systems Incorporated | Arquivos de jogos | Adobe Illustrator File | Adobe Illustrator CC | Adobe Systems Incorporated |
| .AIN | Valve | Arquivos de jogos | Source Engine Compiled AI Nodegraph File | Valve Source SDK | Valve |
| .AIR | Adobe Systems Incorporated | Arquivos de jogos | Adobe AIR Installation Package | Adobe Animate CC 2017 | Adobe Systems Incorporated |
| .AIV | EllaZ Systems | Arquivos de jogos | AIVault Data File | AlVault | EllaZ Systems |
| .AIW | Sony | Arquivos de jogos | Formula One 2001 Game Data | Formula One 2001 | Psygnosis |
| .ALA | Open Source | Arquivos de jogos | Alan Game File | Alan System | Open Source |
| .ALO | LucasArts Entertainment Company, LLC | Arquivos de jogos | Star Wars: Empire At War Game File | Star Wars: Empire at War | LucasArts Entertainment Company, LLC |
| .ALR | Campbell Wild | Arquivos de jogos | ADRIFT Language Resource File | ADRIFT Generator | Campbell Wild |
| .AM1 | Giovanni Albani | Arquivos de jogos | Adventure Maker Project File | Adventure Maker | Giovanni Albani |
| .AMA | Electronic Arts | Arquivos de jogos | FIFA 2000 Game Data | FIFA 2000 | Electronic Arts |
| .AMT | Planit Solutions, Inc. | Arquivos de jogos | Alphacam 3D Mill, 2D Mill Tool | Planit Alphacam | Planit Solutions, Inc. |
| .AR | Microsoft Corporation | Arquivos de jogos | Midtown Madness Data File | 7-Zip | Igor Pavlov |
| .ARC | Symantec Corporation | Arquivos de jogos | Norton Backup Archive | Symantec Norton 360 Version 6.0 | Symantec Corporation |
| .ARC.LH | Nintendo | Arquivos de jogos | Nintendo Archive | Reggie! Level Editor | Treeki And Tempus |
| .ARCH00 | Sierra Entertainment | Arquivos de jogos | F.E.A.R. Game Archive | F.E.A.R | Sierra Entertainment |
| .ARE | BioWare | Arquivos de jogos | BioWare Aurora Engine Area File | BioWare Neverwinter Nights | BioWare |
| .ARKPROFILE | Studio WIldcard | Arquivos de jogos | ARK Game File | Ark: Survival Evolved | Studio WIldcard |
| .ARMY | Microsoft Corporation | Arquivos de jogos | Impossible Creatures Collection Of Created Creatures File | Impossible Creatures | Microsoft Corporation |
| .ARP | ElcomSoft | Arquivos de jogos | Advanced RAR Password Recovery Setup | Advanced Archive Password Recovery | ElcomSoft |
| .ARS | Adobe Systems Incorporated | Arquivos de jogos | After Effects Render Settings File | Adobe After Effects | Adobe Systems Incorporated |
| .ART | Autodesk, Inc. | Arquivos de jogos | ArtCAM Model | ArtCAM | Autodesk, Inc. |
| .ASG | Krisalis Software Limited | Arquivos de jogos | Airport Tycoon Saved Game File | Airport Tycoon | Krisalis Software Limited |
| .ASH | Nintendo | Arquivos de jogos | Nintendo Wii System Menu File | Easy CSM | Open Source |
| .ASS | Ubisoft | Arquivos de jogos | Splinter Cell Blacklist Game Data File | Splinter Cell Blacklist | Ubisoft |
| .ATLAS | Firefly Studios | Arquivos de jogos | Stronghold 3 Editor Data | Stronghold | Firefly Studios |
| .ATM | E-on Software, Inc. | Arquivos de jogos | Vue Atmospheres File | E-on Vue | E-on Software, Inc. |
| .AUR | Andrew Gryc | Arquivos de jogos | AutoREALM Map | AutoREALM | SourceForge |
| .AZP | Atomic Games | Arquivos de jogos | Close Combat Effect Data | Close Combat | Atomic Games |
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