| isv | IDL iTools Saved State |
| isw | Intuit Statement Writer Data |
| isw | ZoneAlarm ForceField Data |
| iswp | iTunes iOS Software Update Data |
| is_ | Compressed ISP File |
| it3 | Internet Timer 3 Log |
| itb | iTunes Database |
| itd | IRIT 3D Data |
| itd | SDL Intermediate Translation Document |
| itdb | iTunes Database |
| ite | iTunes Extras |
| ith | InTether Receiver Package |
| itk | Insight Segmentation and Registration Toolkit Data |
| itl | iTunes Library File |
| itlp | iTunes LP Album Data |
| itm | iThink Model |
| itn | TomTom Route Data |
| itp | e-Record Data File |
| itp | GROMACS Include Topology |
| itpc | iTunes Podcast Link |
| itr | iThink Runtime |
| itss | Microsoft InfoTech Storage System File |
| itt | IconTweaker Theme |
| itv | Nostalgia Emulator Intellivision ROM |
| itw | InTouch With Database |
| itx | IGOR Pro Text File |
| itx | FileNet ITX Form Template |
| itxib | iTunes Dump Data |
| iuc | wyUpdate Client Data |
| iuf | LandMark Incremental Update File |
| iut | SPaCIoS Tool IUT Definition |
| ivd | Bitdefender Antivirus Incremental Database |
| ivl | ILOG JViews Map Data |
| ivm | Avaya Modular Messaging Voice Message |
| ivml | INDENICA Variability Modelling Language Data |