| .A2C | Carnegie Mellon University | 3D Image Files | Alice Object File | Alice | Carnegie Mellon University |
| .A3D | AlternativaPlatform | 3D Image Files | Alternativa Player 3D Export File | AlternativaPlayer | AlternativaPlatform |
| .AAS | Adobe Systems Incorporated | 3D Image Files | Adobe Authorware Shocked Packet File | Adobe Authorware | Adobe Systems Incorporated |
| .ABM FILE EXTENSION | ArcSoft | 3D Image Files | Album File | Konvertor | Logipole |
| .AC | GNU Operating System | 3D Image Files | Autoconf Script | GNU Autoconf | GNU Operating System |
| .ADOC | Stuart Rackham | 3D Image Files | AsciiDoc File | Microsoft Notepad | Microsoft Corporation |
| .AEB | Vero Software | 3D Image Files | Alphacam Wire EDM VB Macro File | Planit Alphacam | Planit Solutions, Inc. |
| .AF | Serif | 3D Image Files | 3DPlus Model | 3DPlus | Serif |
| .AGL | Oracle Corporation | 3D Image Files | Agile XML Archive | Agile Product Lifecycle Management | Oracle Corporation |
| .AM | GNU Operating System | 3D Image Files | Automake Makefile Template | Automake | GNU Operating System |
| .AMF | Autodesk, Inc. | 3D Image Files | Additive Manufacturing File | Autodesk Meshmixer | Autodesk, Inc. |
| .AN8 | Steven Glanville | 3D Image Files | Anim8or File | Anim8or | Steven Glanville |
| .ANIM | Autodesk, Inc. | 3D Image Files | Maya Animation File | Autodesk Maya | Autodesk, Inc. |
| .ANM | Unknown Developer | 3D Image Files | 3D Animation File | CRYENGINE | Crytek |
| .AOF | Abvent Group | 3D Image Files | Artlantis Object File | Artlantis Studio | Abvent Group |
| .AOI | Open Source | 3D Image Files | Art Of Illusion 3D Scene | Art of Illusion | Open Source |
| .APN | Alpine Electronics | 3D Image Files | Alpine Wallpaper | Unknown Software | Unknown Developer |
| .APR | ESRI | 3D Image Files | ArcView Project File | ESRI ArcGIS for Desktop | ESRI (Environmental Systems Research Institute) |
| .ASC | Symantec Corporation | 3D Image Files | PGP (Pretty Good Privacy) ASCII Armored File | Mozilla Thunderbird | Mozilla |
| .ASE | Adobe Systems Incorporated | 3D Image Files | Adobe Swatch Exchange File | Adobe Illustrator CC | Adobe Systems Incorporated |
| .ATF | Molecular Devices | 3D Image Files | Axon Text File | Microsoft Excel | Microsoft Corporation |
| .ATL | Abvent Group | 3D Image Files | Artlantis 3D Scene File | Artlantis Studio | Abvent Group |
| .ATM | E-on Software, Inc. | 3D Image Files | Vue Atmospheres File | E-on Vue | E-on Software, Inc. |
| .AUD | Interscape | 3D Image Files | Video Game Compressed Audio File | Command and Conquer | Interscape |
| .AVT | SavySoda | 3D Image Files | Avatar For iPhone Avatar File | Avatar for iPhone | SavySoda |
| .AWF | Adobe Systems Incorporated | 3D Image Files | Adobe WorkFlow Workgroup Plugin | Adobe Creative Cloud | Adobe Systems Incorporated |
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