| attx | Cadence OrCAD Attributes Data |
| atv | Act! Data File |
| atx | Animation Master Plugin |
| aty | Topicscape Association Type Data |
| atz | Aston Compiled Theme |
| auc | Microsoft Dynamics AX Application Unicode Object Cache |
| aud | GeneMapper Audit Records Data |
| audionote | AudioNote Data |
| audx | ApexSQL Audit Architecture File |
| aue | Annotated Urban Environments Data |
| auf | Audacity Block Data |
| aui | AGE3D UI Editor Color Table |
| aui | ArcSoft MediaImpression UI Data |
| aul | AviUtl Language File |
| aum | Adobe Update Manager Data File |
| aup3-shm | Audacity v3 Temporary Work Data |
| aup3-wal | Audacity v3 Temporary Work Data |
| aur | Aurora Timetable Data |
| aur | AutoREALM Map |
| aus | AutoREALM Symbols |
| aut | Xitami Webserver Password Data |
| autoreg | Mozilla Suite Auto Registration Data |
| autosave | Fusion Autosave |
| aux | LaTeX Auxiliary Data |
| aux | MegaHAL Aux Data |
| aux | MOPAC Auxiliary Results Data |
| aux | PTC Creo Auxiliary Parameter Data |
| aux | VecTor5 Auxiliary Data |
| auz | Ableton Live Authorization |
| ava | Animation Master Model |
| ava | BrainVoyager QX ANCOVA Analysis Data |
| ava3 | AVA CAD/CAM Data |
| avastlic | Avast Antivirus License Data |
| avb | AccPac Plus Macro Archive |
| avc | Avid Media Composer Script |
