| .FMT | Microsoft Corporation | Developer Files | FoxPro Format File | Microsoft Visual FoxPro | Microsoft Corporation |
| .FOOTER | Chuck Shotton | Developer Files | WebSTAR Directory Indexer Footer | WebSTAR | Kerio Technologies |
| .FOR | MacroMates | Developer Files | Fortran 77 Source File | MacroMates TextMate | MacroMates |
| .FP | FileMaker Inc. | Developer Files | FileMaker Pro Spreadsheet | FileMaker Pro | FileMaker Inc. |
| .FPC | Microsoft Corporation | Developer Files | FoxPro Catalog Memo | Microsoft Visual FoxPro | Microsoft Corporation |
| .FPM | The Game Creators | Developer Files | FPS Creator Map File | FBS Creator | The Game Creators |
| .FPP | The Eclipse Foundation | Developer Files | Fortran Source Code | MacroMates TextMate | MacroMates |
| .FPT | Sage | Developer Files | ACT! Data File | Act! | Swiftpage, Inc. |
| .FRM | Oracle Corporation | Developer Files | MySQL Database Format File | MySQL | Oracle Corporation |
| .FRX | Microsoft Corporation | Developer Files | Visual Basic Binary Form File | Microsoft Visual Basic | Microsoft Corporation |
| .FS | Microsoft Corporation | Developer Files | Visual F# Source File | Microsoft Visual Studio | Microsoft Corporation |
| .FSF | Microsoft Corporation | Developer Files | Microsoft Office Cache Data | Microsoft Office | Microsoft Corporation |
| .FSI | Microsoft Corporation | Developer Files | Visual F# Signature File | Microsoft Visual Studio | Microsoft Corporation |
| .FSL | AutoDesSys, Inc. | Developer Files | Form•Z Script | AutoDesSys formZ | AutoDesSys, Inc. |
| .FSSCRIPT | Microsoft Corporation | Developer Files | Visual F# Script File | Microsoft Notepad | Microsoft Corporation |
| .FSX | Microsoft Corporation | Developer Files | Visual F# Script File | Microsoft Notepad | Microsoft Corporation |
| .FTL | Apache Software Foundation | Developer Files | FreeMarker Template File | FreeMaker | Apache Software Foundation |
| .FTN | The Eclipse Foundation | Developer Files | Fortran Source Code | MacroMates TextMate | MacroMates |
| .FW4 | Selections & Functions | Developer Files | Framework IV File | Framework | Selections & Functions |
| .FXC | DIMDATA Co., Ltd | Developer Files | FilePackager Configuration | DIMDATA FilePackager | DIMDATA Co., Ltd |
| .G1M | Casio Computer Co., Ltd. | Developer Files | Casio Model 9860 BASIC Program File | Unknown Software | Unknown Developer |
| .GAB | Open Source | Developer Files | Dencom Global Address Book Export File | Dencom Global Address Book | Open Source |
| .GAR | GIANTS Software | Developer Files | Farming Simulator Game Archive File | Farming Simulator | GIANTS Software |
| .GAS | Atari Corporation | Developer Files | Atari Jaguar GPU Assembly Source | Atari Jaguar | Atari Corporation |
| .GBAP | Dream Design Entertainment Software | Developer Files | GLBasic Project File | GLBasic | Dream Design Entertainment Software |
| .GBL | Ucamco | Developer Files | Gerber Bottom Layer Data File | CadSoft EAGLE | Autodesk, Inc. |
| .GDT | Open Source | Developer Files | Gretl Data File | gretl | Open Source |
| .GED | Thoughtful Creations | Developer Files | GEDCOM Genealogy Data File | Ages! | Jörn Daub e.K. |
| .GEM | RubyGems.org | Developer Files | RubyGems Package | RubyGems | RubyGems.org |
| .GFO | Oracle Corporation | Developer Files | Grammatical Framework | Java | Oracle Corporation |
| .GLADE | Open Source | Developer Files | Glade Project File | Glade | Open Source |
| .GLD | Microchip Technology Inc. | Developer Files | MPLAB C Compiler Linker Script File | MPLAB IDE | Microchip Technology Inc. |
| .GLF | Vladimir Romanyuk | Developer Files | Space Engine Shader File | Space Engine | Vladimir Romanyuk |
| .GLS | Babylon Software Ltd. | Developer Files | Babylon Glossary File | Babylon | Babylon Software Ltd. |
| .GM | GameMonkey | Developer Files | GameMonkey Script | Microsoft Notepad | Microsoft Corporation |
| .GM6 | YoYo Games | Developer Files | GameMaker 6 Project File | GameMaker Studio | YoYo Games |
| .GMD | YoYo Games | Developer Files | Game Maker Program Code | GameMaker Studio | YoYo Games |
| .GMK | YoYo Games | Developer Files | Game Maker Project File | GameMaker Studio | YoYo Games |
| .GML | Galdos Systems, Inc. | Developer Files | Geography Markup Language File | Canvas X | ACD Systems |
| .GMO | GNU Operating System | Developer Files | GNU Machine Object File | GNU gettext | GNU Operating System |
| .GMX | YoYo Games | Developer Files | GameMaker File | GameMaker Studio | YoYo Games |
| .GNI | American Advantech Corporation | Developer Files | VisiDAQ | VisiDAQ | American Advantech Corporation |
| .GNT | Micro Focus International plc | Developer Files | Micro Focus COBOL Generated Code | Visual COBOL | Micro Focus International plc |
| .GO | Google | Developer Files | Go Source Code File | MacroMates TextMate | MacroMates |
| .GOBJ | Geoworks Ensemble | Developer Files | Geoworks Object Code File | Breadbox Office | Breadbox Computer Company |
| .GP | Sublime HQ Pty Ltd | Developer Files | Gofer Project Source | Notepad++ | Don Ho |
| .GPI | Garmin | Developer Files | Garmin Point Of Interest File | Garmin POI loader | Garmin |
| .GPJ | Green Hills Software | Developer Files | MULTI IDE Project File | Green Hills MULTI IDE | Green Hills Software |
| .GR | Geosoft | Developer Files | GX Resource Source File | Oasis montaj | Geosoft |
| .GRADLE | Google | Developer Files | Android Studio Build Data | Android Studio | Google |
| .GROOVY | VMware | Developer Files | Groovy Source Code File | MacroMates TextMate | MacroMates |
| .GRXML | Sublime HQ Pty Ltd | Developer Files | Grammar Data | Sublime Text | Sublime HQ Pty Ltd |
| .GS | Google | Developer Files | Google Apps Script | Google Apps Script | Google |
| .GS3 | GameStarter | Developer Files | GameStarter File | FPSC GameStarter | Unknown Developer |
| .GSS | McGraw-Hill Education | Developer Files | Geometer's Sketchpad Script | Key Curriculum Press Geometer's Sketchpad | McGraw-Hill Education |
| .GST | MapInfo Corporation | Developer Files | MapInfo Geoset File | MapInfo Professional | Pitney Bowes |
| .GWD | Samsung Electronics | Developer Files | Gear Watchface Design File | Samsung Gear Watch Designer | Samsung Electronics |
| .GWF | Benthic Software | Developer Files | Benthic Golden Data File | Benthic Golden | Benthic Software |
| .GXP | Google | Developer Files | Google XML Pages Data | Google XML Pages | Google |
| .GXR | ARTech | Developer Files | GeneXus Report | GeneXus | ARTech |
| .H | The Eclipse Foundation | Developer Files | C/C++/Objective-C Header File | MacroMates TextMate | MacroMates |
| .HAC | Open Source | Developer Files | Helma Actions Script | Helma | Open Source |
| .HAML | Sublime HQ Pty Ltd | Developer Files | HTML Abstraction Markup Language File | Microsoft Notepad | Microsoft Corporation |
| .HAY | Open Source | Developer Files | Haydee Web Server Module Content File | Notepad++ | Don Ho |
| .HBS | GitHub, Inc. | Developer Files | Handlebars Template | Handlebars | GitHub, Inc. |
| .HBX | Open Source | Developer Files | BinHex Encoded File | Smith Micro StuffIt Deluxe | Smith Micro Software |
| .HC | Open Source | Developer Files | VeraCrypt Container File | VeraCrypt | Open Source |
| .HCF | Zaplots Games, Inc. | Developer Files | Compact Ham Library | Zaplots HAM Runtime | Zaplots Games, Inc. |
| .HEX | Intel Corporation | Developer Files | Hexadecimal Source File | Heaventools FlexHex | Heaventools Software |
| .HH | Microsoft Corporation | Developer Files | C++ Header File | Microsoft Notepad | Microsoft Corporation |
| .HHH | Mix Software | Developer Files | Power C Precompiled Header File | Power C Compiler | Mix Software |
| .HHP | Microsoft Corporation | Developer Files | HTML Help Workshop Project | Microsoft HTML Help Workshop | Microsoft Corporation |
| .HISTORY | The Eclipse Foundation | Developer Files | Eclipse IDE Local History Data | Eclipse IDE for Java Developers | The Eclipse Foundation |
| .HM | Microsoft Corporation | Developer Files | Windows Help Context IDs | Microsoft Visual C++ | Microsoft Corporation |
| .HMF | Tech Soft 3D | Developer Files | HOOPS Metafile | HOOPS | Tech Soft 3D |
| .HOC | Open Source | Developer Files | High Order Calculator (HOC) Script File | High Order Calculator (HOC) | Open Source |
| .HPF | IBM | Developer Files | High Performance Fortran File | Microsoft Notepad | Microsoft Corporation |
| .HPP | Microsoft Corporation | Developer Files | C++ Header File | Microsoft Notepad | Microsoft Corporation |
| .HRL | Ericsson Computer Science Laboratory | Developer Files | Erlang Header File | Microsoft Notepad | Microsoft Corporation |
| .HS | Open Source | Developer Files | Haskell Script | MacroMates TextMate | MacroMates |
| .HSC | Aspen Technology, Inc. | Developer Files | Aspen HYSYS Simulation File | Aspen HYSYS | Aspen Technology, Inc. |
| .HSE | Adobe Systems Incorporated | Developer Files | Homesite Snippet End | Adobe Dreamweaver | Adobe Systems Incorporated |
| .HSM | Unknown Developer | Developer Files | Assembly Language Header File | Assembly Programming Language | Unknown Developer |
| .HSP | HeliumScraper.com | Developer Files | Helium Scraper Project File | Helium Scraper | HeliumScraper.com |
| .HTML5 | Sublime HQ Pty Ltd | Developer Files | HTML5 Hypertext Markup Language Revision 5 Source Code | Microsoft Notepad | Microsoft Corporation |
| .HTR | Microsoft Corporation | Developer Files | Microsoft Windows NT Password Services Script | Windows NT | Microsoft Corporation |
| .HWPROJ | Microsoft Corporation | Developer Files | Visual Studio .NET Help Project | Microsoft Visual Basic | Microsoft Corporation |
| .HX | Thermo Fisher Scientific Inc. | Developer Files | Amira 3D Mesh File | Amira | Thermo Fisher Scientific Inc. |
| .HXML | Open Source | Developer Files | HaXe Make File | Haxe | Open Source |
| .HXX | The Qt Company | Developer Files | C++ Source Code Header File | MacroMates TextMate | MacroMates |
| .HZP | Rowley Associates Ltd | Developer Files | CrossWorks For ARM Project | CrossWorks for ARM | Rowley Associates Ltd |
| .H__ | Microsoft Corporation | Developer Files | C++ Header File | Microsoft Notepad | Microsoft Corporation |
| .I | Microsoft Corporation | Developer Files | Visual Studio Intermediate File | Microsoft Visual Studio | Microsoft Corporation |
| .I3 | elego Software Solutions GmbH | Developer Files | Modula-3 Interface Source Code | Modula-3 | elego Software Solutions GmbH |
| .IAP | BioWare | Developer Files | Infinity Engine Add-on Patcher File | Baldur's Gate | BioWare |
| .ICE | Raphaël et Béatrice Mounier | Developer Files | ICE File Archive | ALZip | ESTsoft |
| .IDAPI | Borland | Developer Files | Borland Database Engine IDAPI Data | Borland C++ | Micro Focus International plc |
| .IDB | Microsoft Corporation | Developer Files | Visual Studio Intermediate Debug File | Microsoft Visual Studio | Microsoft Corporation |
| .IDL | Microsoft Corporation | Developer Files | Interface Definition Language File | Microsoft Visual Studio | Microsoft Corporation |
| .IDT | Microsoft Corporation | Developer Files | Windows Installer Database Text Archive File | Windows Installer | Microsoft Corporation |
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