| .I32 | National Instruments | Arquivos de dados | NI LabView Data | LabVIEW | National Instruments |
| .I3C | IBM | Arquivos de dados | IBM Voice Type Languages Newuser File | IBM Voice Type | IBM |
| .I3F | Interactive Intelligence | Arquivos de dados | I3 Fax File | Interaction Fax | Interactive Intelligence |
| .IA6 | Tdata | Arquivos de dados | IApproach Data File | IApproach | Tdata |
| .IAD | Symantec Corporation | Arquivos de dados | Symantec Patch Management Data | Symantec Patch Management | Symantec Corporation |
| .IAR | Krzysztof Wojtas | Arquivos de dados | CD Katalog Data | CD Katalog | Krzysztof Wojtas |
| .IAS | SoftWinter | Arquivos de dados | BitDefender Data File | BitDefender | Bitdefender |
| .IAT | SafetyCulture | Arquivos de dados | iAuditor Template | iAuditor | SafetyCulture |
| .IBA | Lectra | Arquivos de dados | Lectra Clothing Design Pieces File | PAD Pattern | PAD System International Limited |
| .IBG | Lightning UK! | Arquivos de dados | ImgBurn Graph File | DVDINFOPro | Nic and Jonathan Wilson |
| .IBL | Open Source | Arquivos de dados | sIBL System Data | sIBL-Edit | Open Source |
| .IBS | IBM | Arquivos de dados | I2 iBase Data File | i2 iBase | IBM |
| .IBT | Eidos Interactive | Arquivos de dados | Texture And Model File | Deadly Shadows | Eidos Interactive |
| .IBW | WaveMetrics | Arquivos de dados | IGOR Pro Binary Wave Data | IGOR Pro | WaveMetrics |
| .IBX | Interscope s.r.l. | Arquivos de dados | Interscope BlackBox Data | Interscope BlackBox | Interscope s.r.l. |
| .ICD | Macrovision Corporation | Arquivos de dados | SafeDisc Encrypted Program | SafeDisc | Macrovision Corporation |
| .ICG | Bolide Software | Arquivos de dados | Image Comparer Gallery File | Bolide Image Comparer | Bolide Software |
| .ICMS | RagTime.de Development | Arquivos de dados | RagTime Extensions File | RagTime | RagTime.de Development |
| .ICQ | Mail.Ru | Arquivos de dados | ICQ Archive | ICQ | Mail.Ru |
| .ICR | Bolide Software | Arquivos de dados | Image Comparer Result File | Bolide Image Comparer | Bolide Software |
| .ICS | IronCAD, LLC | Arquivos de dados | IronCAD 3D CAD Drawing File | IronCAD | IronCAD, LLC |
| .ICX | Microsoft Corporation | Arquivos de dados | Remote Call Profiler Summary View | Microsoft Windows | Microsoft Corporation |
| .IDA | Microsoft Corporation | Arquivos de dados | Microsoft IIS Server Data | Microsoft IIS | Microsoft Corporation |
| .IDC | Pierre-Emmanuel Gougelet | Arquivos de dados | Core Software Tech IDC File | XnView MP | XnSoft |
| .IDEMO | NetPlay Software | Arquivos de dados | InstantDemo Project File | InstantDemo | NetPlay Software |
| .IDI | Hewlett-Packard | Arquivos de dados | EVA Controller Event Log | Enterprise Virtual Array | Hewlett-Packard |
| .IDK | Anville Instruments | Arquivos de dados | Interface Development Kit Data | Unknown Software | Unknown Developer |
| .IDM | Ulead Systems | Arquivos de dados | Ulead Photo Express Messages File | Ulead Photo Express | Ulead Systems |
| .IDQ | Microsoft Corporation | Arquivos de dados | Microsoft Internet Explorer Data Query File | Internet Explorer | Microsoft Corporation |
| .IDU | BroadVision | Arquivos de dados | Interleaf Desktop Utility Data | Interleaf Desktop Utility | BroadVision |
| .IDY | Micro Focus International plc | Arquivos de dados | Micro Focus Studio Enterprise Edition File | Studio Enterprise Edition | Micro Focus International plc |
| .IE | Genuitec | Arquivos de dados | MyEclipse Image | MyEclipse | Genuitec |
| .IED | CH2M HILL | Arquivos de dados | ISIS Event Data File | ISIS | CH2M HILL |
| .IEE-695 | Hewlett-Packard | Arquivos de dados | IEEE 695 Information PostScript File | Unknown Software | Unknown Developer |
| .IEL | Wondertouch, LLC | Arquivos de dados | ParticleIllusion SE Emitter Library File | particleIllusion | Wondertouch, LLC |
| .IES | Autodesk, Inc. | Arquivos de dados | IES Photometric Data File | AutoCAD Architecture | Autodesk, Inc. |
| .IFI | inFlow Inventory Software | Arquivos de dados | InFlow Inventory File | inFlow Inventory | inFlow Inventory Software |
| .IFM | Shana Corporation | Arquivos de dados | Informed Form Data Document | Shana Informed Filler | Shana Corporation |
| .IFN | WaveMetrics | Arquivos de dados | IGOR Pro Formatted Notebook File | IGOR Pro | WaveMetrics |
| .IFS | InfoSlips | Arquivos de dados | InfoSlips Package | InfoSlips | InfoSlips |
| .IFT | Canon Inc. | Arquivos de dados | Canon Settings Data | Unknown Software | Unknown Developer |
| .IFX | IBM | Arquivos de dados | Rational XDE Data | Rational Rose | IBM |
| .IG | elego Software Solutions GmbH | Arquivos de dados | Modula-3 Generic Interface Source | Modula-3 | elego Software Solutions GmbH |
| .IGC | Open Source | Arquivos de dados | Anime List Builder Input File | Anime List Builder | Open Source |
| .IGN | Adobe Systems Incorporated | Arquivos de dados | RoboHelp Ignore List File | Adobe RoboHelp | Adobe Systems Incorporated |
| .IGNORE | Unknown Developer | Arquivos de dados | Ignored Data File | Unknown Software | Unknown Developer |
| .II | Axialis Company | Arquivos de dados | IconWorkshop Extended Information File | Axialis IconWorkshop | Axialis Company |
| .IIE | Unknown Developer | Arquivos de dados | SimIIe Emulator Data | SimIIe - SimSystem IIe | Unknown Developer |
| .IIF | Intuit, Inc. | Arquivos de dados | Intuit Interchange Format File | Microsoft Excel | Microsoft Corporation |
| .III | Insurance Information Institute, Inc. | Arquivos de dados | Know Your Stuff File | Know Your Stuff | Insurance Information Institute, Inc. |
| .IIL | Symantec Corporation | Arquivos de dados | Norton CleanSweep Installation Log File | Microsoft Notepad | Microsoft Corporation |
| .IKLAX | Squirrels | Arquivos de dados | AirParrot Media Data | AirParrot | Squirrels |
| .IKM | Open Source | Arquivos de dados | XWE Data | XWE | Open Source |
| .IKS | Microsoft Corporation | Arquivos de dados | Microsoft InkSeine Document File | InkSeine | Microsoft Corporation |
| .IL | Microsoft Corporation | Arquivos de dados | MSIL Assembler Input File | Microsoft Visual Studio | Microsoft Corporation |
| .IL3 | Wondertouch, LLC | Arquivos de dados | ParticleIllusion 3 Emitter Library | particleIllusion | Wondertouch, LLC |
| .ILD | Open Source | Arquivos de dados | XWE Data | XWE | Open Source |
| .ILF | Open Source | Arquivos de dados | Alim File | Alim | Open Source |
| .ILG | Flexera Software | Arquivos de dados | InstallScript Log File | Unknown Software | Unknown Developer |
| .ILJ | Honest Technology | Arquivos de dados | Honestech VHS To DVD Project | honestech VHS to DVD | Honest Technology |
| .ILOGICVB | Autodesk, Inc. | Arquivos de dados | iLogic VB File | Autodesk Inventor | Autodesk, Inc. |
| .ILR | Unity Technologies | Arquivos de dados | Unity 3D License Request | Unity Technologies Unity | Unity Technologies |
| .ILV | IBM Cognos | Arquivos de dados | ILOG File | ILOG CPLEX Optimization Studio | IBM |
| .ILX | Andrew Quilley | Arquivos de dados | Interlex Vocabulary Data | Interlex | Andrew Quilley |
| .IMA | Sage | Arquivos de dados | Sage ACT! Email Message | Act! | Swiftpage, Inc. |
| .IMAGE | Apple | Arquivos de dados | Apple Disk Image | Roxio Toast 15 | Roxio |
| .IMB | Perion Network Ltd | Arquivos de dados | IncredMail Address Book And Temporary Contacts Data | IncrediMail | Perion Network Ltd |
| .IMD | Various Developers | Arquivos de dados | GIS Image Metadata File | ESRI ArcGIS for Desktop | ESRI (Environmental Systems Research Institute) |
| .IMF | id Software | Arquivos de dados | Id Music File | CocoModX | Open Source |
| .IMH | Perion Network Ltd | Arquivos de dados | IncrediMail contacts Export File | IncrediMail | Perion Network Ltd |
| .IMK | Perion Network Ltd | Arquivos de dados | IncrediMail License | IncrediMail | Perion Network Ltd |
| .IMP | Lotus Software | Arquivos de dados | Improv Spreadsheet File | Lotus 1-2-3 | IBM |
| .IMR | IBM | Arquivos de dados | Impromptu Report File | IBM Cognos Impromptu | Symitar |
| .IMS | CursorArts Company | Arquivos de dados | IconForge Create Executable Library Data | IconForge | CursorArts Company |
| .IMT | Intuit, Inc. | Arquivos de dados | My Time Data File | macOS | Apple |
| .IN | Bitplane | Arquivos de dados | SmartGENERATOR Template File | smartGenerator | Bitplane |
| .IN3 | Harvard Graphics | Arquivos de dados | Harvard Graphics Input Device Driver File | Harvard Graphics ChartXL | Harvard Graphics |
| .IN4 | Phixsoft | Arquivos de dados | InfoBlaster IN4 Registry File | InfoBlaster IN4 | Phixsoft |
| .INA | Microsoft Corporation | Arquivos de dados | MS-DOS Data File | MS-DOS | Microsoft Corporation |
| .INDEX | The Eclipse Foundation | Arquivos de dados | Eclipse Help Index | Eclipse CDT | The Eclipse Foundation |
| .INI | Microsoft Corporation | Arquivos de dados | Windows Initialization File | Notepad++ | Don Ho |
| .INK | Mimio | Arquivos de dados | Mimio Ink Data File | MimioStudio | Mimio |
| .INP | Concept Software | Arquivos de dados | Urdu InPage Document | Urdu InPage | Concept Software |
| .INS | Open Source | Arquivos de dados | LaTeX Installer Script | Microsoft Notepad | Microsoft Corporation |
| .INSID | Apple | Arquivos de dados | Golden Orchard Apple II CD Rom File | Apple OS X | Apple |
| .INST | Interscape | Arquivos de dados | RMCProfile Peak Profile Data | RMCProfile | Interscape |
| .INSTALLER | Apple | Arquivos de dados | Golden Orchard Apple II CD Rom File | Apple OS X | Apple |
| .INSTALLLOG | Microsoft Corporation | Arquivos de dados | Microsoft .NET Installation Log | Microsoft Visual Studio | Microsoft Corporation |
| .INSTR | Unknown Developer | Arquivos de dados | Unknown Apple II File. (found On Golden Orchard Apple II CD Rom) | Atom | GitHub, Inc. |
| .INTEGER | Apple | Arquivos de dados | Golden Orchard Apple II CD Rom File | Apple OS X | Apple |
| .INTRO | Unknown Developer | Arquivos de dados | Unknown Apple II File. (found On Golden Orchard Apple II CD Rom) | Atom | GitHub, Inc. |
| .INV | Copyboy | Arquivos de dados | INVedit File | INVedit | Copyboy |
| .INVENTOR | Open Source | Arquivos de dados | SGI Open Inventor File | Open Inventor | Open Source |
| .IP | Stardock Corporation | Arquivos de dados | Icon Packager Theme File | Stardock Icon Packager | Stardock Corporation |
| .IPJ | Autodesk, Inc. | Arquivos de dados | Inventor Project File | Autodesk Inventor | Autodesk, Inc. |
| .IPR | Flexera Software | Arquivos de dados | InstallShield Project | InstallShield | Flexera Software |
| .IQC | International TechneGroup Incorporated | Arquivos de dados | CADIQ Comparison Analysis Result | CADIQ | International TechneGroup Incorporated |
| .IQF | IRIS | Arquivos de dados | Integra Query File | Integra | IRIS |
| .IQR | International TechneGroup Incorporated | Arquivos de dados | CADIQ View Analysis Results | CADIQ | International TechneGroup Incorporated |
| .IQS | International TechneGroup Incorporated | Arquivos de dados | CADIQ Summary File | CADIQ | International TechneGroup Incorporated |
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