| irl | HomeVision Infrared Signal Data |
| irl | AMX IR File |
| irn | IRedit Database |
| irock | intelliRock Sensor Data |
| irr | UVBrewer Irradiance File |
| irt | IRIT 3D Model |
| irt | Graphicon Interactive RealTime PHIGS |
| irtp | Graphicon Interactive RealTime PHIGS |
| irx | Brewer Lamp Irradiance File |
| is3 | SmartWare Input-Screen File |
| isale | iSale Auction Data |
| isam | ISAM Database |
| iscf | Intel Schematic Connectivity Format Data |
| ise | InstallShield Express File |
| isg | HSC Chemistry Solgasmix Solver Data |
| isi | Web of Science Databases Output |
| isk | Druvaa inSync Client Key |
| isl | Inno Setup List |
| ism | ISAM Database |
| isml | IIS Smooth Streaming Publishing Point Definition |
| ispc | Image Surfer Pro Collection |
| isr | InstallShield Uninstall Information |
| istg | Imagine Staging File |
| isv | IDL iTools Saved State |
| isw | Intuit Statement Writer Data |
| isw | ZoneAlarm ForceField Data |
| iswp | iTunes iOS Software Update Data |
| is_ | Compressed ISP File |
| it3 | Internet Timer 3 Log |
| itb | iTunes Database |
| itd | SDL Intermediate Translation Document |
| itd | IRIT 3D Data |
| itdb | iTunes Database |
| ite | iTunes Extras |
| ith | InTether Receiver Package |