| apf | Adobe Profile Format File |
| apg | PowerADA APG File |
| api | Adobe Photoshop Ink Colors Setup |
| apkg | Anki Exported Flashcard Deck |
| aplibrary | Apple Aperture Library |
| apm | Alphacam Punch Param Macro |
| app | Alphacam Punch Post Data |
| appcache | HTML5 Application Cache |
| apple | Apple AppleSingle Data |
| application | ClickOnce Deployment Manifest |
| apr | Gerber Aperture Data |
| apr_lib | Altium Designer Aperture Library Data |
| apt | Nimbus 7 SAMS APRIORI Data |
| apt | Gerber Aperture Data |
| apt | Alphacam Punch Tool Data |
| apvr | BenMAP APV Configuration Results |
| apw | AnyPassword Data File |
| aq | Ancestral Quest Database |
| aq1 | AptiQuiz Test |
| aqa | Ancestral Quest Database Index |
| aqa | AptiQuiz Test Result |
| aqc | AquaChem Database |
| aqg | BenMAP Air Quality Grid |
| aqm | AlpineQuest Map |
| ar0 | MyDOS Ramdisk Image |
| ar1 | MyDOS Ramdisk Image |
| ar2 | MyDOS Ramdisk Image |
| ar3 | MyDOS Ramdisk Image |
| ar4 | MyDOS Ramdisk Image |
| ar5 | MyDOS Ramdisk Image |
| ar6 | MyDOS Ramdisk Image |
| ar7 | MyDOS Ramdisk Image |
| ar8 | MyDOS Ramdisk Image |
| ar9 | MyDOS Ramdisk Image |
| ara | Archivaldo Resource Archive |
