| .DD | Sage | Developer Files | Sage MAS 90 Data File | Sage MAS 90 | Sage |
| .DDD | Alpha Software | Developer Files | Alpha Five Data Dictionary File | Alpha Anywhere - Alpha Software | Alpha Software |
| .DDM | Alpha Software | Developer Files | Alpha Five Data Dictionary Memo File | Alpha Anywhere - Alpha Software | Alpha Software |
| .DDP | Embarcadero Technologies | Developer Files | Delphi Diagram Portfolio File | Delphi (IDE) | Embarcadero Technologies |
| .DDX | Alpha Software | Developer Files | Alpha Five Data Dictionary Index File | Alpha Anywhere - Alpha Software | Alpha Software |
| .DEC | Various Developers | Developer Files | Declaration File | Microsoft Notepad | Microsoft Corporation |
| .DEF | Microsoft Corporation | Developer Files | Module Definition File | Microsoft Visual Studio | Microsoft Corporation |
| .DEP | Microsoft Corporation | Developer Files | Windows Dependency File | Microsoft Windows | Microsoft Corporation |
| .DEPLOY | Just Great Software | Developer Files | DeployMaster Installation Project File | DeployMaster | Just Great Software |
| .DEV | Bloodshed Software | Developer Files | Dev-C++ Project File | Dev-C++ | Bloodshed Software |
| .DF1 | Omnis Software | Developer Files | Omnis Native Datafile | Omnis Studio | Omnis Software |
| .DFAC | Unknown Developer | Developer Files | DreamFactory ActiveX Control | DreamFactory | Open Source |
| .DFB | Interscape | Developer Files | Data Flask Formula | Interscape Data Flask | Interscape |
| .DFD | Open Source | Developer Files | ABC Dyadic Functions Data | ABC Programming langauge | Open Source |
| .DFM | Open Source | Developer Files | Pascal File | Notepad++ | Don Ho |
| .DFWEBAPPLICATION | TogetherSoft | Developer Files | Together ControlCenter Development Tool | Together | TogetherSoft |
| .DG | Data Access Worldwide | Developer Files | DataFlex Source Code For A Dialog Box | DataFlex | Data Access Worldwide |
| .DGD | Unknown Developer | Developer Files | DGD Program | Dworkin's Game Driver | Open Source |
| .DGML | Microsoft Corporation | Developer Files | Visual Studio Directed Graph Document | Microsoft Visual Studio | Microsoft Corporation |
| .DGSL | Microsoft Corporation | Developer Files | Microsoft Visual Studio Visual Shader Graph File | Microsoft Visual Studio | Microsoft Corporation |
| .DIAGSESSION | Microsoft Corporation | Developer Files | Diagnostics Session File | Internet Explorer | Microsoft Corporation |
| .DIFF | Matt Mackall | Developer Files | Patch File | Mercurial | Matt Mackall |
| .DIN | 4ThePeople Limited | Developer Files | DataEase Installation Script | DataEase | 4ThePeople Limited |
| .DLG | Crytek | Developer Files | Crysis Dialogue Data File | Crysis | Crytek |
| .DMB | BYOND | Developer Files | BYOND Game Executable | BYOND | BYOND |
| .DMD | Oracle Corporation | Developer Files | SQL Developer Data Modeler File | SQL Developer Data Model | Oracle Corporation |
| .DML | Sybase, Inc | Developer Files | DynaScript File | Internet Explorer | Microsoft Corporation |
| .DMT | DeLorme | Developer Files | XMap Transfer File | XMap | Garmin |
| .DOB | Sublime HQ Pty Ltd | Developer Files | Visual Basic UserDocument | Notepad++ | Don Ho |
| .DOR | Graphisoft | Developer Files | ArchiCAD Geometric Description Language File | ARCHICAD | Graphisoft |
| .DOX | Microsoft Corporation | Developer Files | Visual Basic Binary UserDocument | Microsoft Visual Studio | Microsoft Corporation |
| .DPJ | Delft Spline Systems | Developer Files | DeskProto Project | DeskProto | Delft Spline Systems |
| .DPK | Embarcadero Technologies | Developer Files | Delphi Package | Delphi (IDE) | Embarcadero Technologies |
| .DPL | Embarcadero Technologies | Developer Files | Delphi Package Library | Delphi (IDE) | Embarcadero Technologies |
| .DPR | Niklaus Wirth | Developer Files | Pascal Source Code | MacroMates TextMate | MacroMates |
| .DRC | Open Source | Developer Files | Open Mobile Alliance DRM Rights Object | Microsoft Notepad | Microsoft Corporation |
| .DRES | Embarcadero Technologies | Developer Files | Delphi Compiled Resource File | Delphi (IDE) | Embarcadero Technologies |
| .DS | DAZ 3D | Developer Files | DAZ Studio 1/2 Script | DAZ Studio | DAZ 3D |
| .DSB | Dell Technologies | Developer Files | Dell DataSafe Backup File | DataSafe Local Backup | Dell Technologies |
| .DSK | Power Software Ltd | Developer Files | General Disk Image | PowerISO | Power Software Ltd |
| .DSP | Open Source | Developer Files | Dynamic Studio Professional Module | ModPlug Player | Open Source |
| .DSR | Activision | Developer Files | Modern Warfare 3 Dedicated Server Recipe File | Call of Duty 4: Modern Warfare | Activision |
| .DSU | Schneider Electric | Developer Files | ProWORX Nxt Data Setup | ProWORX | Schneider Electric |
| .DTD | Syncro Soft | Developer Files | Document Type Definition File | Microsoft Notepad | Microsoft Corporation |
| .DTS | CyberLink | Developer Files | DTS Encoded Audio File | CyberLink PowerDVD | CyberLink |
| .DVB | Autodesk, Inc. | Developer Files | AutoCAD VBA Project File | AutoCAD VBA module | Autodesk, Inc. |
| .DWS | Autodesk, Inc. | Developer Files | AutoCAD Drawing Standards File | Autodesk AutoCAD | Autodesk, Inc. |
| .DYLIB | Apple | Developer Files | Mach-O Dynamic Library | Apple Xcode | Apple |
| .E | OpenEuphoria | Developer Files | Euphoria Include File | Rapid Deployment Euphoria | OpenEuphoria |
| .EAF | Max Planck Institute for Psycholinguistics | Developer Files | ELAN Annotation Format | ELAN | Max Planck Institute for Psycholinguistics |
| .EBC | SourceForge | Developer Files | MediaBASIC Compiled Project | MediaBASIC | SourceForge |
| .EBS | Psychology Software Tools, Inc. | Developer Files | E-Run Version 1 Script File | E-Prime | Psychology Software Tools, Inc. |
| .EBX | IBM | Developer Files | Rational Rose 98 Compiled Script | Rational Rose | IBM |
| .EC | Informix Corporation | Developer Files | Informix ESQL/C Source | IBM Informix | IBM |
| .ECP | Intelitek | Developer Files | EasyC Project File | EasyC | Intelitek |
| .ECT | Yozosoft | Developer Files | Yozo Office Chart Template File | Yozosoft Yozo Office | Yozosoft |
| .EDM | Adobe Systems Incorporated | Developer Files | Adobe Extension Data Markup Language File | Adobe Dreamweaver | Adobe Systems Incorporated |
| .EDML | Adobe Systems Incorporated | Developer Files | Adobe Extension Data Markup Language File | Adobe Dreamweaver | Adobe Systems Incorporated |
| .EDMX | Microsoft Corporation | Developer Files | ADO.NET Entity Data Model Designer File | Microsoft Visual Studio | Microsoft Corporation |
| .EEP | Open Source | Developer Files | EEPROM Data File | HHD Hex Editor | HHD Software |
| .EFD | Parallels | Developer Files | Parallels Desktop Related File | Parallels Desktop for Mac | Parallels |
| .EFG | Open Source | Developer Files | Gambit Extensive Game Format | Gambit | Open Source |
| .EKM | Symbol Dynamics LLC | Developer Files | EXP Macro | EXP | Symbol Dynamics LLC |
| .EL | GNU Project | Developer Files | Emacs Lisp Code File | GNU Emacs | GNU Project |
| .ELA | TradeStation | Developer Files | EasyLanguage Archive | TradeStation | TradeStation |
| .ELC | GNU Project | Developer Files | Emacs Compiled Lisp File | GNU Emacs | GNU Project |
| .ELD | DIAL | Developer Files | Eulumdat Formatted Luminaire Data File | DIAL DIALux | DIAL |
| .ELK | Altium | Developer Files | Altium Designer Linker Error Message | Altium Designer | Altium |
| .EMV | National Instruments | Developer Files | LabVIEW Configuration File | LabVIEW | National Instruments |
| .ENT | Syncro Soft | Developer Files | External Entity | Oxygen XML Editor 19 | Syncro Soft |
| .EPJ | Grass Valley | Developer Files | EDIUS Pro Project File | Thomson EDIUS | Grass Valley |
| .EQN | Altium | Developer Files | GAL Equation File | Altium Designer | Altium |
| .ERB | Open Source | Developer Files | Ruby ERB Script | Microsoft Notepad | Microsoft Corporation |
| .ERL | INCA Internet | Developer Files | GameGuard Error Log File | GameGuard | INCA Internet |
| .ES | Interscape | Developer Files | ECHOSPEECH File | ECHOSPEECH | Interscape |
| .EU | OpenEuphoria | Developer Files | Euphoria Include Data | Rapid Deployment Euphoria | OpenEuphoria |
| .EW | OpenEuphoria | Developer Files | Euphoria Source Code File | Microsoft Notepad | Microsoft Corporation |
| .EX | Symantec Corporation | Developer Files | Norton Ghost Template Data | Symantec Ghost Solution Suite | Symantec Corporation |
| .EXE_ | Open Source | Developer Files | Emu8086 Assembly Source Code | 8086 Microprocessor Emulator | Open Source |
| .EXL | SysTools Solutions | Developer Files | Export Lister File | SysTools Export Notes | SysTools Solutions |
| .EXP | Unknown Developer | Developer Files | Symbols Export File | Microsoft Visual Studio | Microsoft Corporation |
| .EXU | Open Source | Developer Files | Euphoria For Linux Source Code | Euphoria | Open Source |
| .EXW | OpenEuphoria | Developer Files | Euphoria Source Code File | Microsoft Notepad | Microsoft Corporation |
| .F | The Eclipse Foundation | Developer Files | Fortran Source Code | MacroMates TextMate | MacroMates |
| .F# | Microsoft Corporation | Developer Files | F# Source Code File | F# | Microsoft Corporation |
| .F03 | The Eclipse Foundation | Developer Files | Fortran Source Code | MacroMates TextMate | MacroMates |
| .F40 | Digital Equipment Corporation | Developer Files | PDP-10 FORTRAN-4 Compiler Source File | PDP-10 | Digital Equipment Corporation |
| .F77 | Intel Corporation | Developer Files | Fortran 77 Language Source File | Intel Fortran Compiler | Intel Corporation |
| .F90 | Intel Corporation | Developer Files | Fortran 90 Source Code File | Absoft Pro Fortran | Absoft Corporation |
| .F95 | Open Source | Developer Files | Fortran 95 Source Code File | Absoft Pro Fortran | Absoft Corporation |
| .FACES | Oracle Corporation | Developer Files | FacesServlet Page | JavaServer Faces | Oracle Corporation |
| .FACTOR | Factor Community | Developer Files | Factor Language Source File | Factor | Factor Community |
| .FBP | Open Source | Developer Files | WxFormBuilder Project | wxWidgets | Open Source |
| .FCE | EaSynth Solution | Developer Files | ForeUI Custom Element File | EaSynth Solution ForeUI | EaSynth Solution |
| .FCL | EaSynth Solution | Developer Files | ForeUI Custom Library File | EaSynth Solution ForeUI | EaSynth Solution |
| .FDM | Microsoft Corporation | Developer Files | Exchange Forms Designer Form Message | Microsoft Exchange Server | Microsoft Corporation |
| .FGL | Fifth Generation Systems | Developer Files | Fifth Generation Language Source File | Notepad++ | Don Ho |
| .FILTERS | Microsoft Corporation | Developer Files | Visual C++ Project Filters File | Microsoft Visual Studio | Microsoft Corporation |
| .FLA | Adobe Systems Incorporated | Developer Files | Adobe Animate Animation | Adobe Animate CC 2017 | Adobe Systems Incorporated |
| .FMB | Oracle Corporation | Developer Files | Oracle Forms Binary Source Code | Oracle Forms | Oracle Corporation |
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