| animeproj | Anime Studio Project |
| anjuta | Anjuta DevStudio Project |
| ap12 | Siemens TIA v12 Project |
| ap13 | TIA Portal v13 Project |
| ap14 | TIA Portal v14 Project |
| ap15 | SIMATIC WinCC v15 Project |
| ap16 | TIA Portal v16 Project |
| ap3 | Asprova Project |
| apj | Archibus Project Preferences Data |
| apj | Autodesk AutoCAD Architecture Project |
| approj | ActivePresenter Project |
| apr | Apadana Project |
| aprj | ApacheConf Project |
| aproj | Leapfrog Geo Project |
| apt | appTranslator Project |
| apz | Autoplay Media Studio Exported Project |
| argo | ArgoUML Project |
| arh | Siemens ProTool Compressed Project |
| art42 | Bernina Explorations v1.x Project |
| art50 | Bernina Embroidery Software v5.0 Design |
| art60 | Bernina Embroidery Software v6.0 Design |
| artproj | Artifacts for Visual Studio Project |
| artx | Artisteer Project |
| as2proj | FlashDevelop Project |
| as3proj | FlashDevelop Project |
| ashprj | Ashampoo Burning Studio Project |
| asmproj | Atmel Studio Assembler Project |
| asprj | Altova XMLSpy Scripting Project |
| asproj | Visual Studio Analysis Services Project |
| asta | Astah Project |
