| is4 | SmartWare Input-Screen File |
| isale | iSale Auction Data |
| isallic | iSale License Data |
| isam | ISAM Database |
| iscf | Intel Schematic Connectivity Format Data |
| iscorrupt | Skype Corrupted Data |
| isd | Altair FEKO Calculated Field Distribution Data |
| isdb | iThink Database |
| ise | InstallShield Express File |
| iset | ARToolKit NFT Image Set |
| isg | HSC Chemistry Solgasmix Solver Data |
| ish1 | Animation-ish Wiggledoodle-ish Document |
| ish2 | Animation-ish FlipBook-ish Document |
| ish3 | Animation-ish Advanced-ish Document |
| 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 | IRIT 3D Data |
| itd | SDL Intermediate Translation Document |
| itdb | iTunes Database |
| ite | iTunes Extras |
| item | DM Genie Item Data |
| itemdata-ms | Windows 8 Start Screen Item Data |