| Extension | File Type | Files scanned | Contributor |
| I3F | I3 Fax file | 8 | |
| IAF | Outlook 97 and 2000 E-mail Account Settings | 18 | Roberto 'rbnet' Bolli |
| IBK | Imaging for Windows Image Bookmark | 9 | |
| IBK | Sound Blaster Instrument Bank | 2 | |
| IBP | IsoBuster CD/DVD image backup | 2 | |
| ICA | Citrix Independent Computer Architecture file | 12 | |
| ICC | Art Icons Pro - IconCollection | 7 | mishka |
| ICE | Freeze! compressed archive | 2 | |
| ICE | ICE compressed archive | 4 | |
| ICL | Icons Library | 20 | |
| ICM | Indipendent Color Matching profile | 53 | |
| ICN | HP Palmtop 100/200LX Icon | 6 | |
| ICNS | Icons resource file | 18 | |
| ICO | OS/2 Icon | 320 | |
| ICO | Windows Icon | 547 | |
| ICPR | Art Icons Pro - IconProject | 9 | mishka |
| ICR | NCSA Telnet Interactive Color Raster bitmap | 4 | |
| ICS/VCS | iCalendar - vCalendar | 5 | |
| IDE | Borland C++ Project definition | 2 | |
| IDE | Grand Theft Auto III model IDs and properties | 12 | |
| IDF | Microsoft Instrument Definition File | 2 | |
| IDM | Fahrenheit - The Game - DAT + IDM archive | 2 | |
| IDOL | IDle Object Library - bytecode | 3 | |
| IDW | AutoDesk Inventor drawing | 14 | |
| IDX | Java Applet cache index | 916 | |
| IDX | VobSub Index file | 25 | |
| IES | IESNA Photometric data | 12 | |
| IFF | "The Sims" object | 30 | |
| IFF | Amiga IFF 16SVX Audio | 13 | |
| IFF | Amiga IFF 8SVX Audio | 98 | |
| IFF | Maya IFF bitmap | 3 | |
| IFF/ILBM/LBM | IFF InterLeaved BitMap | 73 | |
| IFF/SMUS | IFF-SMUS Music | 44 | |
| IFO | DVD Info file | 26 | |
| IGR | Intergraph SmartSketch Drawing | 15 | |
| IGS/IGES | Initial Graphics Exchange Specification (IGES) data | 16 | |
| IIF | QuickBooks Import/Export Interchange File | 114 | |
| ILD | ILDA image data transfer format | 4 | |
| ILK | Microsoft Linker Database | 20 | |
| ILM | Opus Creator multimedia file | 18 | |
| ILX | Interlex vocabulary | 22 | |
| IMA | IncrediMail animation | 23 | |
| IMB | IncrediMail Address Book | 4 | |
| IME | IncrediMail emoticon | 4 | |
| IMF | IncrediMail letter/ecard | 54 | |
| IMG | Digital Research GEM VDI bitmap | 15 | |
| IMG | GEM Paint Rle bitmap | 12 | |
| IMG | Garmin Mapsource Img (actual compressed maps) | 2033 | Graham Rose |
| IMG | Garmin basemap | 6 | |
| IMG | Img Software Set bitmap | 14 | |
| IMG | QEMU qcow disk image | 2 | |
| IMG | ScreenBuilder image | 9 | Paul Panks |
| IMG/RLE | ADEX bitmap | 44 | |
| IMG3 | Img3 enctrypted signed container | 2 | |
| IMI | IncrediMail image | 118 | |
| IMN | IncrediMail notifier | 8 | |
| IMO | iMON Setting file | 50 | |
| IMOVIEPROJ | iMovie project | 30 | |
| IMOVIEPROJ | iMovie project (old ver.) | 20 | |
| IMP | Softbook eBook | 8 | |
| IMP | WinImp compressed archive | 22 | |
| IMR | Impromptu report | 10 | |
| IMR | Information Magic data file | 5 | |
| IMS | IMS Content Package | 9 | |
| IMS | IncrediMail skin | 3 | |
| IMW | IncrediMail sound (MIDI music) | 13 | |
| IMW | IncrediMail sound (WAV) | 13 | |
| IMY/IMELODY | iMELODY sound/music | 11 | |
| IMY/IMELODY | iMELODY sound/music (header less) | 3 | |
| IMZ | Compressed Disk Image (password protected) | 12 | |
| IMZ | WinImage compressed disk image | 75 | |
| IN | CFAST input - data | 3 | |
| INDD | InDesign Document | 50 | |
| INF | Autorun.inf file | 6 | Thaimodz |
| INFO | Amiga icon file (NewIcons type) | 835 | Ruggero Furlanetto |
| INFO | GNU Info document | 33 | |
| INFO | ZbThumbnail.Info | 11 | |
| INI | Generic INI configuration | 17 | |
| INI | Microsoft QBX local INI | 19 | |
| INI | Windows Boot Loarder information | 14 | |
| INP | InPage document | 8 | |
| INS | InstallShield Script | 14 | |
| INX | InstallShield Compiled Rules | 23 | |
| IP | IconPackager theme | 20 | |
| IP | Interactive Physics data | 8 | |
| IPD | BlackBerry Backup file | 4 | |
| IPE | Microth Stroke Set | 22 | |
| IPF | Interchangeable Preservation Format floppy disk image | 45 | |
| IPJ | Autodesk Inventor project | 5 | |
| IPK | Nintendo DS Packed Images | 3 | |
| IPR | InstallShield Project | 17 | |
| IPS | International Patching System binary patch | 4 | |
| IPT | Inventor Part file | 15 | |
| IPX | Ipix Spherical Panorama | 26 | |
| IQY | Microsoft Web query | 21 | |
| IRP | InfraRecorder Project | 8 | |
| ISF | Inspiration Software data | 23 | |
| ISF | Tektronix instrument data file | 2 | |
| ISM | ISAM table handler data | 7 | Vincent van der Tuin |
| ISM | ITI SimulationX Encrypted Model | 63 | TBeu |
| ISO | ISO CDImage - universal format e.g. WinISO or IsoBuster | 27 | THE LoW |
| ISS | Inno Setup Script | 13 | Christian Blackburn |
| ISS | Inno Setup Script (with rem) | 37 | Christian Blackburn |
| ISS | InstallShield Response File | 12 | |
| ISS/XARC | ISS Audio | 3 | |
| IST | Adobe Image Styler file | 10 | |
| ISTG | Imagine Staging File | 4 | |
| ISU | InstallShield Uninstall Script | 18 | |
| ISZ | ISo Zipped format | 4 | |
| IT | Impulse Tracker module | 27 | |
| ITA | IconTweaker theme | 5 | |
| ITC | iTunes CoverFlow data file | 12 | |
| ITL | iTunes Music Library | 6 | |
| ITR | Icy Tower Replay | 165 | |
| IUM | infoUSA Network Meter file | 9 | |
| IV | SGI Open Inventor file | 22 | |
| IVF | Intel Indeo Video File | 14 | |
| IVR | RealNetworks Internet Video Recording | 6 | |
| IVU | ImmerVision XML user interface | 5 | |
| IW2 | Information Workshop 2000 data file | 9 | |
| IWC | WaveL bitmap | 21 | |
| IWD | Call Of Duty map - game data archive | 11 | |
| IWS | Information Workshop data file | 3 | |
| IXL | DB/TextWorks Database Indexed List | 7 | |
