| idx | Galactic IDX Library |
| Intuit Quicken Index Data |
| LaTeX Unsorted Index Data |
| Microsoft Outlook Express Mailbox Index |
| Microsoft SQL Server Constraints |
| PTC Creo Instance Index Data |
| SmartWare Index Data |
| Sunnysoft InterWrite Index Data |
| Treepad Database Index |
| idz | Autodesk Inventor Compressed Content Library |
| I-DEAS Data |
| ie | MyEclipse Image |
| ie3 | Internet Explorer Related Data |
| ied | ISIS Event Data File |
| ief | iCE CFR Raw Data |
| ISIS Control File |
| iei | Image Eye Index Cache |
| iel | ParticleIllusion SE Emitter Library |
| iem | Informix Error Message |
| ienv | iData 3 Envelope Template Data |
| ies | IESNA Photometric Data |
| ie_ | Compressed IEC File |
| if90 | Programmer's Notepad Data |
| ifaith | iFaith SHSH Data |
| ifc | Industry Foundation Classes Data |
| ifczip | Compressed IFC Data |
| ifd | Adobe Output Designer Form |
| iff | SmartWare Temporary Merge Data |
| ifi | inFlow Inventory Database Backup |
| ifiction | Zoom iFiction File |
| ifl | Autodesk 3D Studio Max Image File List |
| iflv | InfoLevin Database |
| ifm | Brighterion iPrevent Fraud Model |
| RSView Machine Edition Information Message |
| Shana Informed Filler Form Data |
| ifn | IGOR Pro Formatted Notebook File |
| ifo | ImageForge Pro Graphic Object Layer Data |
| RSView Machine Edition Information Setup Data |
| ifol | Instant File Opener Data |
| ifp | KnowledgeMan Script |
| ifs | Ant Movie Catalog Script |
| FractInt IFS File |
| InfoSlips Package |
| OS/2 Warp Installable Filesystem Data |
| ift | BSL Inverse Fourier Transform Data |
| 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 |
| IOCOM Visimeet Data |
| igma | INTUS Terminal Graph Mask Archive |
| ign | Adobe RoboHelp Ignore List |
| 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 |
| ihand | iClone Hand Data |
| 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 |
| iif | Shana Informed Filler Interchange Document |
| iii | Know Your Stuff File |
| iil | Norton CleanSweep Installation Log |
| iio | CoreFSIF IO Stream Data |
