| idpp | Adobe InDesign Preflight Profile |
| idrc | Adobe InDesign Resource |
| idrm | Tekla ID Mapping File |
| idroo | IDroo Data |
| idsp | eXtendable Wad Editor IDSP Data |
| idu | Interleaf Desktop Utility |
| idvi | eXtendable Wad Editor IDVI Data |
| idx | Canon ZoomBrowser EX Database Index |
| idx | Citrix Program Neighborhood Database Index |
| idx | dBASE Database Index |
| idx | Easy Timesheets Index Data |
| idx | Galactic IDX Library |
| idx | Intuit Quicken Index Data |
| idx | LaTeX Unsorted Index Data |
| idx | Microsoft Outlook Express Mailbox Index |
| idx | Microsoft SQL Server Constraints |
| idx | PTC Creo Instance Index Data |
| idx | SmartWare Index Data |
| idx | Sunnysoft InterWrite Index Data |
| idx | Treepad Database Index |
| idz | Autodesk Inventor Compressed Content Library |
| idz | I-DEAS Data |
| ie | MyEclipse Image |
| ie3 | Internet Explorer Related Data |
| ied | ISIS Event Data File |
| ief | iCE CFR Raw Data |
| ief | ISIS Control File |
| iei | Image Eye Index Cache |
| iel | ParticleIllusion SE Emitter Library |
| iem | Informix Error Message |
