| .GUIKIT | Unsanity | Indstillingsfiler | ShapeShifter Theme File | ShapeShifter | Unsanity |
| .GWS | Intergraph Corporation | Indstillingsfiler | GeoMedia GeoWorkspace File | Intergraph GeoMedia | Hexagon Geospatial |
| .GXT | Rockstar Games | Indstillingsfiler | Grand Theft Auto Text File | Grand Theft Auto III | Rockstar Games |
| .H | The Eclipse Foundation | Indstillingsfiler | C/C++/Objective-C Header File | MacroMates TextMate | MacroMates |
| .HCM | IBM | Indstillingsfiler | IBM HCM Configuration File | z/OS and z/VM Hardware Configuration Manager (HCM) | IBM |
| .HDP | Microsoft Corporation | Indstillingsfiler | HD Photo File | Adobe Photoshop | Adobe Systems Incorporated |
| .HDT | Adobe Systems Incorporated | Indstillingsfiler | Photoshop HDR Toning Preset File | Adobe Photoshop CC | Adobe Systems Incorporated |
| .HELPCFG | Adobe Systems Incorporated | Indstillingsfiler | Adobe AIR Help Configuration | Adobe AIR | Adobe Systems Incorporated |
| .HEP | Novell, Inc. | Indstillingsfiler | Help Librarian Data | NetWare | Novell, Inc. |
| .HFP | The Plugin Site | Indstillingsfiler | Harrys Filters Preset | Harry's Filters | The Plugin Site |
| .HID | Sony | Indstillingsfiler | Sony Ericsson Remote Settings File | Sony Ericsson PC Suite | Sony Mobile Communications |
| .HLX | Advanced Micro Devices, Inc. | Indstillingsfiler | ATI Radeon Video Driver Support File | ATI Catalyst | Advanced Micro Devices, Inc. |
| .HME | Microsoft Corporation | Indstillingsfiler | Windows Mobile Theme File | Microsoft ActiveSync | Microsoft Corporation |
| .HNF | Frans Nijhuis (Zekitez Freeware) | Indstillingsfiler | HNF Split & Merge Channels File | HNF Split & Merge | Frans Nijhuis (Zekitez Freeware) |
| .HNS | Han Kleijn | Indstillingsfiler | HNS Settings File | Hallo Night Sky | Han Kleijn |
| .HOW2 | Visma | Indstillingsfiler | Visma Performit Player Configuration File | Visma Performit Player | Visma |
| .HPR | Adobe Systems Incorporated | Indstillingsfiler | Internal RoboHelp File | Adobe RoboHelp | Adobe Systems Incorporated |
| .HRV | Commodore International | Indstillingsfiler | Personal Paint Croatian Language User Interface File | Personal Paint | Amiga |
| .HT | Hilgraeve Inc | Indstillingsfiler | HyperTerminal Session File | HyperTerminal | Hilgraeve Inc |
| .HTS | Open Source | Indstillingsfiler | HyperTuner Skin | HyperTuner | Open Source |
| .HWT | Huawei | Indstillingsfiler | Huawei Emotion UI Theme | EMUI | Huawei |
| .HXA | Microsoft Corporation | Indstillingsfiler | Microsoft Help Attribute Definition | Microsoft Visual Studio | Microsoft Corporation |
| .HXW | Microsoft Corporation | Indstillingsfiler | Microsoft Help Attribute Definition | Microsoft Visual Studio | Microsoft Corporation |
| .IAF | Microsoft Corporation | Indstillingsfiler | Outlook Internet Account File | Microsoft Outlook 2016 | Microsoft Corporation |
| .IBL | Open Source | Indstillingsfiler | sIBL System Data | sIBL-Edit | Open Source |
| .IC | elego Software Solutions GmbH | Indstillingsfiler | Modula-3 M3CG Intermediate Language File | Modula-3 | elego Software Solutions GmbH |
| .ICA | Citrix Systems | Indstillingsfiler | Citrix Independent Computing Architecture File | Citrix Receiver | Citrix Systems |
| .ICC | Corel | Indstillingsfiler | International Color Consortium Profile File | Adobe Photoshop CC | Adobe Systems Incorporated |
| .ICD | Macrovision Corporation | Indstillingsfiler | SafeDisc Encrypted Program | SafeDisc | Macrovision Corporation |
| .ICM | Adobe Systems Incorporated | Indstillingsfiler | Image Color Matching Profile | Adobe Photoshop | Adobe Systems Incorporated |
| .ICP | AT&T Labs | Indstillingsfiler | Unix IContact Parameter Data | Unix | AT&T Labs |
| .ICW | Microsoft Corporation | Indstillingsfiler | Microsoft Internet Explorer Internet Connection Wizard Data | Internet Explorer | Microsoft Corporation |
| .IDF | Don Ho | Indstillingsfiler | MIDI Instrument Definition File | Microsoft Notepad | Microsoft Corporation |
| .IDI | Hewlett-Packard | Indstillingsfiler | EVA Controller Event Log | Enterprise Virtual Array | Hewlett-Packard |
| .IFB | Oracle Corporation | Indstillingsfiler | Oracle Siebel Interface Configuration File | Siebel eBusiness | Oracle Corporation |
| .IFT | Canon Inc. | Indstillingsfiler | Canon Settings Data | Unknown Software | Unknown Developer |
| .IGN | Adobe Systems Incorporated | Indstillingsfiler | RoboHelp Ignore List File | Adobe RoboHelp | Adobe Systems Incorporated |
| .IGR | Interscape | Indstillingsfiler | Igor Engraver File | Igor Engraver | Interscape |
| .IIT | Clickteam | Indstillingsfiler | Install Creator Project File | Install Creator | Clickteam |
| .IKF | PCS Systemtechnik GmbH | Indstillingsfiler | INTUS Keyboard Settings File | INTUS Terminals | PCS Systemtechnik GmbH |
| .IKMP | IK Multimedia | Indstillingsfiler | SampleTank Preset | SampleTank | IK Multimedia |
| .IMESX | Microsoft Corporation | Indstillingsfiler | Microsoft Office IME Search Provider Definition File | Microsoft Office | Microsoft Corporation |
| .IMO | SoundGraph, Inc | Indstillingsfiler | iMON Manager Settings File | iMON Manager | SoundGraph, Inc |
| .IMS | CursorArts Company | Indstillingsfiler | IconForge Create Executable Library Data | IconForge | CursorArts Company |
| .INF | Parametric Technology Corporation | Indstillingsfiler | Pro/ENGINEER Temporary | Pro/ENGINEER | PTC |
| .INI | Microsoft Corporation | Indstillingsfiler | Windows Initialization File | Notepad++ | Don Ho |
| .INO | Jordan Russell | Indstillingsfiler | Inno Setup Script | Microsoft Notepad | Microsoft Corporation |
| .INS | Open Source | Indstillingsfiler | LaTeX Installer Script | Microsoft Notepad | Microsoft Corporation |
| .IN_ | Microsoft Corporation | Indstillingsfiler | Microcoft Setup Information Data | Microsoft Windows | Microsoft Corporation |
| .IPCC | Apple | Indstillingsfiler | iPhone Carrier Bundle | Apple iTunes | Apple |
| .IPL | Rockstar Games | Indstillingsfiler | GTA Item Placement File | Grand Theft Auto III | Rockstar Games |
| .IRL | IBM | Indstillingsfiler | IBM WebSphere ILOG JRules Rule File | IBM WebSphere ILOG JRules | IBM |
| .IRS | Adobe Systems Incorporated | Indstillingsfiler | Adobe Save For Web Settings | Adobe Illustrator CC | Adobe Systems Incorporated |
| .ISC | Xilinx, Inc. | Indstillingsfiler | Xilinx Device Configuration File | Xilinx Platform Studio (XPS) | Xilinx, Inc. |
| .ISP | Microsoft Corporation | Indstillingsfiler | IIS Internet Service Provider Settings | Microsoft IIS | Microsoft Corporation |
| .ISS | Jordan Russell | Indstillingsfiler | Inno Setup Script | Microsoft Notepad | Microsoft Corporation |
| .ITC | Apple | Indstillingsfiler | iTunes Cover Flow Data File | Apple iTunes | Apple |
| .IX | Corel | Indstillingsfiler | Corel WordPerfect Office Template File | Corel WordPerfect | Corel |
| .JDF | Adobe Systems Incorporated | Indstillingsfiler | Adobe Acrobat Job Definition File | Adobe Acrobat DC | Adobe Systems Incorporated |
| .JEQ | Cowon Systems | Indstillingsfiler | JetAudio Equalizer Settings | jetAudio | Cowon Systems |
| .JFF | Freedom Scientific | Indstillingsfiler | JAWS INI Data | JAWS | Freedom Scientific |
| .JGP | Jolly Giant Inc | Indstillingsfiler | QWS3270 PLUS Session Parameter Data | QWS3270 PLUS | Jolly Giant Inc |
| .JMD | Corel | Indstillingsfiler | Corel PaintShop Pro Image Map Settings | PaintShop Pro | Corel |
| .JOBS | Open Source | Indstillingsfiler | VirtualDub Job File | VirtualDub | Open Source |
| .JPL | Sonic Foundry | Indstillingsfiler | Siren Jukebox File | Siren Jukebox | Sonic Foundry |
| .JSD | Jazer Solutions | Indstillingsfiler | Jazer Data File | Jazer | Jazer Solutions |
| .JSF | Adobe Systems Incorporated | Indstillingsfiler | Java Script Command File | Adobe Fireworks | Adobe Systems Incorporated |
| .JSM | Mozilla | Indstillingsfiler | Firefox JavaScript Module | Mozilla Firefox | Mozilla |
| .JSR | HASP Online, LLC | Indstillingsfiler | Job Safety Report Definition File | JSA Generator | HASP Online, LLC |
| .JUDO | Sublime HQ Pty Ltd | Indstillingsfiler | JudoScript Source Code | Sublime Text | Sublime HQ Pty Ltd |
| .JWS | Oracle Corporation | Indstillingsfiler | Java Web Services File | WebLogic | Oracle Corporation |
| .KBD | Autodesk, Inc. | Indstillingsfiler | 3ds Max Keyboard Shortcuts File | Autodesk 3ds Max | Autodesk, Inc. |
| .KBM | Manuel Op De Coul | Indstillingsfiler | Scala Keyboard Mapping | Scala | Manuel Op De Coul |
| .KBP | Keirsey Group | Indstillingsfiler | Keirsey-Bates Temperament Sorter Profile | Keirsey-Bates Temperament Sorter | Keirsey Group |
| .KCF | William Miles | Indstillingsfiler | KiSS Configuration File | Kisekae Set System (KiSS) | William Miles |
| .KCI | Microsoft Corporation | Indstillingsfiler | Visual Studio .NET DB Project Indexing Settings | Microsoft Visual Studio | Microsoft Corporation |
| .KDR | Thermo Fisher Scientific Inc. | Indstillingsfiler | Kinetica Installation Data | Kinetica | Thermo Fisher Scientific Inc. |
| .KDS | Knyzhov Dmitry | Indstillingsfiler | KD Player Skin File | Microsoft Notepad | Microsoft Corporation |
| .KEY | Unknown Developer | Indstillingsfiler | License/ Encrypted Security Key File | Avira Antivirus Pro 2016 | Avira Operations GmbH & Co. KG. |
| .KFP | Adobe Systems Incorporated | Indstillingsfiler | Adobe Acrobat Preflight Profile File | Adobe Acrobat DC | Adobe Systems Incorporated |
| .KIK | Apple | Indstillingsfiler | Golden Orchard Apple II CD Rom File | Apple OS X | Apple |
| .KLC | Microsoft Corporation | Indstillingsfiler | Microsoft Keyboard Layout Creator Keyboard Data | Microsoft Keyboard Layout Creator | Microsoft Corporation |
| .KNT | SourceForge | Indstillingsfiler | KeyNote Note File | Keynote | SourceForge |
| .KOF | Borland | Indstillingsfiler | Kylix Options Data | Borland Kylix | Borland |
| .KPF | ActiveState | Indstillingsfiler | Komodo Project File | ActiveState Komodo IDE | ActiveState |
| .KPL | Phrogsoft | Indstillingsfiler | Kids Programming Language Source Code | Phrogram | Phrogsoft |
| .KSF | Pandora Tv | Indstillingsfiler | KMPlayer Skin File | KMPlayer | Pandora Tv |
| .KUIP | Kingsoft | Indstillingsfiler | Kingsoft Office Personalization File | WPS Office | Kingsoft |
| .KVT | Open Source | Indstillingsfiler | KVIrc Heme | KVIrc | Open Source |
| .KWS | KeyWallet GbR | Indstillingsfiler | KeyWallet Skin | KeyWallet | KeyWallet GbR |
| .KWT | Open Source | Indstillingsfiler | KVIrc Theme | KVIrc | Open Source |
| .KX | Ruud Van Velsen | Indstillingsfiler | KiXtart Tokenized Script | KixTart | Ruud Van Velsen |
| .KYB | Software AG | Indstillingsfiler | Keyboard Layout | Entire Connection | Software AG |
| .KYS | Adobe Systems Incorporated | Indstillingsfiler | Adobe Photoshop Keyboard Shortcuts File | Adobe Illustrator CC | Adobe Systems Incorporated |
| .L4D | MAXON Computer | Indstillingsfiler | Cinema 4D Layout File | MAXON Cinema 4D | MAXON Computer |
| .L64 | Commodore International | Indstillingsfiler | 64LAN Image File | Unknown Software | Unknown Developer |
| .LANG | Mojang | Indstillingsfiler | Minecraft Language File | Microsoft Notepad | Microsoft Corporation |
| .LAUNCH | Rogue Wave | Indstillingsfiler | Zend Studio Debugger Configuration Data | Eclipse IDE for Java Developers | The Eclipse Foundation |
| .LAY | Tecplot, Inc | Indstillingsfiler | Tecplot Layout File | Tecplot 360 | Tecplot, Inc |
| .LAYOUT | Apple | Indstillingsfiler | Apple MainStage Layout Data | Logic Studio | Apple |
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