| Abbreviation | Definition |
|---|---|
| AST | Adobe Color Separtion table (Adobe PhotoShop) |
| AST | Astound multimedia file |
| AST | Claris Works ASsistanT file |
| ASW | ACD See Slide Show Project File |
| ASX | Advanced Streaming Format Video |
| ASX | Cheyenne Backup script |
| AT2 | Aldus Persuasion 2.0 Auto Template |
| ATK | Bitmap graphics (Andrew Toolkit Raster Object file) |
| ATM | Adobe Type Manager related file |
| ATT | AT&T Group 4 file - Bitmap graphics |
| AU | Sound - basic 8-bit compressed audio file |
| AUD | AUDio File |
| AUT | IPIX Automation file |
| AUX | ChiWriter AUXiliary dictionary |
| AUX | TeX/LaTeX AUXiliary references |
| AVA | Avagio Publication file |
| AVB | AntiViral Toolkit Pro Bases |
| AVI | Audio Video Interleaved file |
| AVR | Audio Visual Research file format Sound file |
| AVS | Application Visualization System (animation) |