| acq | AcqKnowledge Data |
| acq | AcqURL Bookmark Database |
| acr | ACRobot Script |
| acr | Audio Comparer Results Data |
| acr | Autodesk Simulation Mechanical Concrete Cracking Data |
| acr | Medlin Payroll Software Accrual Method Adjustments Data |
| acrodata | Adobe Acrobat Data File |
| acrotheme | Adobe Acrobat Theme Data |
| acrs | Adobe Authorware Internal Data |
| acrypt | AutoCrypt Blowfish Encrypted Document |
| acrypx | AutoCrypt AES Encrypted Document |
| acrypz | AutoCrypt AES Encrypted Document |
| acs | Microsoft Agent Character |
| acs | Vox Proxy Animated Character Data |
| acs2 | AIMP 2 Skin File |
| acs3 | AIMP 3 Skin File |
| acsm | Adobe Content Server Manager Data |
| act | Adobe Photoshop Color Table |
| act | Alma act/cut Data |
| act | Animation Master Animation Data |
| act | Genesis3D Actor Data |
| act | OptionVue Portfolio Manager Account Data |
| act | RSView Machine Edition Accound Data |
| act3d | SpinFire Reader ACT3D Data |
| actc | Actions Collection Data |
| actions | PhotoLine 4 Defaults Data |
| actm | Autodesk AutoCAD Action Macro |
| actor | Amazon Lumberyard Actor Data |
| acv | Adobe Photoshop Custom Curve |
| ac_ | CaseWare Working Papers Compressed Client File |
| ad | After Dark Screensaver |
| ad3e | Adobe Dimension for Mac Data |
| ada | ActiveDocs Opus Document |
| adb | Act! Database |
| adb | Adlib Express Server Data |
