| abc | Business Card Maker Document |
| abd | Worksheet Crafter Document |
| abs | Abs Spreadsheet |
| abt | ED-IT PC AsIs Braille Text File |
| abw | AbiWord Document |
| ac | AC3D Model |
| ac3d | AC3D Model |
| ac5 | ArtCut 5 Document |
| ac6 | ArtCut 6 Document |
| accd | Microsoft Access 2007 Database |
| accdb | Microsoft Access 2007 Database |
| accdc | Microsoft Access 2007 Signed Package |
| accde | Microsoft Access 2007 Executable |
| accdr | Microsoft Access 2007 Run-time |
| accdt | Microsoft Access 2007 Database Template |
| accdw | Microsoft Access 2007 Database Link |
| accfl | Microsoft Access Field Template |
| accft | Microsoft Access 2007 Data Type Template |
| ad65 | Adobe PageMaker 6.5 for Mac Document |
| adb | Ability Database Document |
| add | Alphacam Diecut Drawing |
| ade | Microsoft Access Project Extension |
| adoc | Authentica Secure Office Protected Word Document |
| adoc | AsciiDoc File |
| ados | ADOS Compound Document |
| adox | ActivDox Document |
| adsk | Autodesk Exchange File |
| ad_asm | Alibre Design CAD Assembly Document |
| ad_bom | Alibre Design Bills of Material Data |
| ad_drw | Alibre Design 2D CAD Drawing |