| df6 | Omnis Studio v6 Database |
| dfac | DreamFactory ActiveX Control |
| dfd | ABC Dyadic Functions Data |
| dfm | Delphi Form |
| dfn | Delphi Definition File |
| dg | DataFlex Dialog Box Source Code |
| dg5 | DGLux5 Page |
| dgd | DGD Program |
| dge | Micro Focus Studio Declaration Generator Batch File |
| dgml | Directed Graph Markup Language Document |
| dgrp | Retro Studios Dependency Group |
| dgsl | Directed Graph Shader Language Data |
| dgx | IBM Rational XDE Diagram |
| di | D Language Source Code |
| dif | ProWorx NXT Data Interchange File |
| dill | Dart Compiled Binary |
| din | DataEase Installation Script |
| dip | Crestron SIMPL IP Table Data |
| disco | Visual Studio .NET Discovery Data |
| discomap | Visual Studio .NET Discovery Map Data |
| dj | DJGPP Source Code |
| dj2 | DJGPP Source Code |
| djg | DJGPP Makefile |
| dl3 | VS10XX VSOS Application |
| dlct | AppleScript Dialect Data |
| dldi | libfat Dynamically Linked Device Interface |
| dlg | Visual C++ Dialog |
| dlk | Transputer Development System Occam Compiler Link Info |
| dm | BYOND Dream Maker Source Code |
| dm1 | ER/Studio Data Model |