| inst | RMCProfile Instrument Data |
| int | STK Interval List File |
| int | Molpro Permanent Integral Data |
| int | Tinker Internal Coordinates |
| int | Nostalgia Emulator Intellivision ROM |
| int | Gaussian Two-Electron Integral File |
| interface | Notepad++ Interface Data |
| intlib | Altium Designer Integrated Library |
| inx | PCCharge Request XML File |
| in_ | Compressed INI File |
| iobit | Advanced SystemCare Rollback Data |
| iod | Sony DVGate IO Data |
| iof | FindIt Data Fle |
| iok | Omniscope IOK Data |
| iom | Omniscope IOM Data |
| iom | Bosch VisualMotion IO Mapper Data |
| ios | Apple iOS Related Data |
| iox | Response Channel Manager Template |
| ipalias | Apple iPhoto Alias File |
| ipc | IPC-D-356 Data |
| ipe | Microth InPad Stroke Set |
| ipf | IGOR Pro Procedure File |
| ipf | F-Secure Incremental Policy File |
| iphoto | Apple iPhoto Photo Library |
| ipi | Microsoft Windows Installer Data |
| ipkg | Indicore SDK Package |
| iplb | Apple iPhoto Library File |
| ipm | Image-Pro Plus Macro |
| ipmeta | Apple iPhoto Metadata |
| ipp | OmniPage Image Enhancement Template |
| ipr | TINA Interpreter File |
| ips | VisualBoy Advance IPS Patch File |
| ipspot | Apple iPhoto Spot File |
| iptc | IPTC Photo Metadata |
| iptheme | IconPackager Raw Theme Data |