| asc | ASCII Armored GPG/PGP File |
| asc | Plain Text Document |
| ascii | Plain Text Document |
| asd | Alphacam Stone Drawing |
| asd | Microsoft Word AutoRecovery File |
| ase | Autodesk 3D Studio ASCII Scene Export |
| aseprite | Aseprite Sprite Data |
| asm | Solid Edge Assemblies Document |
| assbin | Allegorithmic Substance Painter Scene |
| ast | ClarisWorks Assistant |
| astx | Adobe Story Exported Script |
| asy | Asymptote Document |
| at2 | Aldus Persuasion v2 Template |
| at65 | Adobe PageMaker for Mac 6.5 Template |
| atd | Alphacam Lathe Drawing |
| atom | Atom Syndication Format File |
| atw | AnyTime Organizer Deluxe Document |
| av | Final Draft AV v1 Document |
| avery | Avery Design and Print Online Label |
| aw | Applixware Words Document |
| awd | Ability Draw Document |
| awd | Microsoft Fax Image |
| awg | Ability Draw Vector Graphic |
| awp | Ability Write Template |
| aws | Ability Spreadsheet Document |
| awss | Microsoft Works for Mac Spreadsheet |
| awt | AbiWord Template |
| aww | Ability Write Document |
| awwp | Microsoft Works for Mac Document |
| ax3 | Apex Sketch v3 Document |
| ax5 | Apex Sketch v5 Document |
| axz | Apex Sketch v6 Document |
| b4u | docPointer Visual ReadMe Document |
| bakx | MakeMusic Finale Notation Backup |
| ban | Broderbund PrintMaster Banner |