39 File Extensions starting with A
| .A52 | Dolby Digital AC-3 Compressed Audio File |
| .A64 | Artist 64 Image |
| .AAC | Advanced Audio Coding Compressed Audio File |
| .ABS | Optocat Image |
| .ABT | AbiWord Template |
| .ABW | AbiWord Document |
| .AC3 | Dolby Digital AC-3 Compressed Audio File |
| .ACE | Ace Compressed Archive |
| .ACE | Aces200 Image |
| .ACR | Dicom Image |
| .AFX | Auto F/X Image |
| .AIF | Audio Interchange Format File |
| .ALIAS | Alias Image File |
| .ALS | Alias Image File |
| .AMI | Amica Paint Image |
| .ANI | Animated Mouse Cursor Image |
| .ANI | Windows Animated Cursor |
| .ANV | AirNav Image |
| .APE | Monkey's Audio Compressed Audio File |
| .APX | Photopaint Image |
| .ARF | ARF Image |
| .ARJ | Archived by Robert Jung Compressed Archive |
| .ARN | Astronomical Research Network Image |
| .ART | Art Director Image |
| .ART | Artisan Image |
| .ART | Advanced Art Studio Image |
| .ART | Pfs Art Publisher Image |
| .ASA | ASP Configuration File |
| .ASAX | ASP.Net Open XML Configuration File |
| .ASF | Advanced Systems Format Video |
| .ASP | Active Server Page Source File |
| .ASPX | ASP.Net Open XML Source File |
| .ASX | Advanced Stream Redirector |
| .ATK | Andrew Toolkit raster object Image |
| .ATT | AT&T Group 4 Image |
| .AU | Sun / NeXT Audio File |
| .AU3 | AutoIt Script |
| .AVI | Audio Video Interleave |
| .AVS | Stardent AVS X Image |