| igtx | IGOR Pro Text |
| igv | Integrative Genomics Viewer Data |
| igw | Interactive Groundwater Modeling Data |
| iha | Proficy Historian Archive |
| ihc | Proficy Historian Configuration |
| ihw | IN-HEH Timeline Workspace |
| ihx | IN-HEH Timeline Database |
| ii | IconWorkshop Extended Information |
| iic | ISIS Initial Conditions Data |
| iid | Instantiated IED Description Data |
| iie | SimSystem IIe Emulator Data |
| iii | Know Your Stuff File |
| iil | Norton CleanSweep Installation Log |
| iis | Panasonic Camcorder IIS Metadata |
| iix | SDL Trados Translation Memory Index |
| ijg | Independent JPEG Group Related Data |
| ike | IKE-Scan Data |
| ikn | IKinema Rig Data |
| il3 | ParticleIllusion 3 Library |
| ild | ILDA Frames |
| ilda | ILDA Frames |
| ileaf | Interleaf Desktop |
| ilf | Alim Data File |
| ilg | LaTeX Index Generation Log |
| ilht | Mac OS X Finder Internet HTTP Location |
| ilm | MotionTracking Illumination Correction Data |
| ilp | Gurobi Optimizer Temporary Data |
| ilr | Unity License Request File |
| ils | RFM Instrument Line Shape File |
| ilx | Interlex Vocabulary Data |
| im4m | IMG4 Signature Data |
| im4p | IMG4 Payload Data |
| ima | Zemax Image Surface Data |
| imap | IceWarp Mail Server IMAP Data |
| imb | IncrediMail Address Book |