| ief | ISIS Control File |
| iei | Image Eye Index Cache |
| iel | ParticleIllusion SE Emitter Library |
| ienv | iData 3 Envelope Template Data |
| ies | IESNA Photometric Data |
| ie_ | Compressed IEC File |
| ifaith | iFaith SHSH Data |
| ifc | Industry Foundation Classes Data |
| ifczip | Compressed IFC Data |
| iff | SmartWare Temporary Merge Data |
| ifi | inFlow Inventory Database Backup |
| ifiction | Zoom iFiction File |
| iflv | InfoLevin Database |
| ifn | IGOR Pro Formatted Notebook File |
| ifol | Instant File Opener Data |
| ifs | FractInt IFS File |
| ifs | InfoSlips Package |
| 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 | IOCOM Visimeet Data |
| igm | Indigo Material Data |
| igma | INTUS Terminal Graph Mask Archive |
| ign | Adobe RoboHelp Ignore List |
| igs | Indigo Renderer Scene |
| 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 |