| ifs | Ant Movie Catalog Script |
| ifs | FractInt IFS File |
| ifs | InfoSlips Package |
| ifs | OS/2 Warp Installable Filesystem Data |
| ift | BSL Inverse Fourier Transform Data |
| ift | IGOR Pro Formatted Notebook Template File |
| ifw | INTUS Terminal Firmware |
| ig | iSpy Event Data |
| igb | Google Earth Model File |
| igc | Anime List Builder Data |
| igd | TIBCO Spotfire Graph Definition |
| igl | inSORS Grid Layout File |
| igm | Indigo Material Data |
| igm | IOCOM Visimeet Data |
| igma | INTUS Terminal Graph Mask Archive |
| ign | Adobe RoboHelp Ignore List |
| ign | ICQ Ignore List |
| igq | Indigo Queue Data |
| igr | Igor Engraver Data |
| igs | Indigo Renderer Scene |
| igt | ImageGadget Template |
| igtheme | ImageGlass Theme |
| igtx | IGOR Pro Text |
| igv | Integrative Genomics Viewer Data |
| igw | Interactive Groundwater Modeling Data |
| iha | Proficy Historian Archive |
| ihc | Proficy Historian Configuration |
| ihs | Bink Inbound History Data |
| ihw | IN-HEH Timeline Workspace |
| ihx | IN-HEH Timeline Database |
| ii | IconWorkshop Extended Information |
| iib | Lotus Notes Incremental Backup Data |
| iic | ISIS Initial Conditions Data |
| iid | Instantiated IED Description Data |
| iie | SimSystem IIe Emulator Data |
