| arc | I-DEAS Archive |
| arc | LH ARC Compressed Archive |
| arc | Norton Backup Archive |
| arc | Symbian OS Backup Archive |
| archiver | Incredible Bee Archiver Arhive |
| arduboy | Arduboy Game Package |
| arj | ARJ Compressed Archive |
| ark | PowerDesk Pro Archive |
| arn | CD Autorun Creator Package |
| arprojpkg | Spark AR Studio Project Package |
| asar | ASAR Archive |
| asdb | Asphyre Sphinx v2 Archive File |
| asec | Android Secure External Cache |
| ashbak | Ashampoo Backup Archive |
| ask | Astrotite 200X Skin Data |
| aspk | My APK App Backup Package |
| asr | Asura Engine Audio Streaming Archive |
| asvf | Asphyre Sphinx v1 Archive File |
| ate | Microsoft Accounting Accountants Transfer |
| ati | Microsoft Accounting Import |
| atlas | Exient XGS Atlas Archive |
| avastsounds | Avast Antivirus Sound Package |
| avasttheme | Avast Antivirus Theme Data |
| avgsounds | AVG Internet Security Sound Package |
| awb | CRIWARE AWB Package |
| awi | AIM Widget Package |
| aza | ProSystem fx Engagement Admin Package |
| azp | ProSystem fx Engagement Binder Package |
| b1 | B1 Compressed Archive |
| b6z | B6Zip Archive |
