| .AAF | Avid Technology | Videotiedostot | Advanced Authoring Format File | Adobe After Effects | Adobe Systems Incorporated |
| .ACW | Microsoft Corporation | Videotiedostot | Windows Accessibility Wizard File | Microsoft Windows Accessibility Wizard | Microsoft Corporation |
| .AEC | MAXON Computer | Videotiedostot | Cinema 4D After Effects Import Composition File | MAXON Cinema 4D | MAXON Computer |
| .AEP | Adobe Systems Incorporated | Videotiedostot | After Effects Project | Adobe After Effects | Adobe Systems Incorporated |
| .AET | Adobe Systems Incorporated | Videotiedostot | After Effects Project Template | Adobe After Effects | Adobe Systems Incorporated |
| .AETX | Adobe Systems Incorporated | Videotiedostot | After Effects XML Project Template | Adobe After Effects | Adobe Systems Incorporated |
| .AJP | Interscape | Videotiedostot | CCTV Video File | AJP Player | Interscape |
| .ALE | Avid Technology | Videotiedostot | Avid Log Exchange File | Microsoft Notepad | Microsoft Corporation |
| .AM | GNU Operating System | Videotiedostot | Automake Makefile Template | Automake | GNU Operating System |
| .AMC | Pegasys | Videotiedostot | AMC Video File | Apple QuickTime Player | Apple |
| .AMV | VideoLAN | Videotiedostot | Anime Music Video File | VLC Media Player | VideoLAN |
| .AMX | Valve | Videotiedostot | AMX Mod Plugin File | Half-Life | Valve |
| .ANIM | Autodesk, Inc. | Videotiedostot | Maya Animation File | Autodesk Maya | Autodesk, Inc. |
| .ARF | Cisco Systems | Videotiedostot | WebEx Advanced Recording File | Cisco WebEx Player | Cisco Systems |
| .ASF | Microsoft Corporation | Videotiedostot | Advanced Systems Format File | Microsoft Windows Media Player | Microsoft Corporation |
| .ASX | Microsoft Corporation | Videotiedostot | Microsoft ASF Redirector File | VLC Media Player | VideoLAN |
| .AVB | Avid Technology | Videotiedostot | Avid Bin File | Avid Media Composer | Avid Technology |
| .AVC | Kaspersky Lab | Videotiedostot | Kaspersky Virus Database File | Kaspersky Anti-Virus | Kaspersky Lab |
| .AVD | Magix Software GmbH | Videotiedostot | Movie Edit Pro Video Information File | MAGIX Movie Edit Pro | Magix Software GmbH |
| .AVF | SourceForge | Videotiedostot | Avermedia Recorded Video Backup | Project X | SourceForge |
| .AVH | Pioneer DJ Corporation | Videotiedostot | Pioneer AVH Firmware Update | Pioneer AVH | Pioneer DJ Corporation |
| .AVI | Microsoft Corporation | Videotiedostot | Audio Video Interleave File | Microsoft Windows Media Player | Microsoft Corporation |
| .AVM | VideoLAN | Videotiedostot | Anime Music Video File | VLC Media Player | VideoLAN |
| .AVP | Avid Technology | Videotiedostot | Avid Project File | Avid Media Composer | Avid Technology |
| .AVS | Adobe Systems Incorporated | Videotiedostot | Adobe Photoshop Variations File | Adobe Photoshop | Adobe Systems Incorporated |
| .AWLIVE | PYsoftware | Videotiedostot | Active Webcam Video File | PY Software Active Webcam | PYsoftware |
| .AXM | AXMEDIS Products and Services | Videotiedostot | AXMEDIS Object | AXMEDIS Editor | AXMEDIS Products and Services |
| .AXV | CSIRO | Videotiedostot | Annodex Video File | Macgo Mac Media Player | Macgo International |
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