| dcf | WRAP Daily Flows Columnar Data |
| dck | Resolume Deck |
| dcl | DesignComposer Design Command Language File |
| dcl | DumpSec Report |
| dcm | DiskCatalogMaker Catalog Data |
| dcmd | DiskCatalogMaker Thumbnail-Enabled Catalog Data |
| dcmf | DiskCatalogMaker Catalog Data |
| dcn | Autodesk AutoCAD Civil 3D Depth Slope Definition |
| dcn | VerdiCash Digital Cash Note |
| dcover | Belight Disc Cover Data |
| dcpie | DocumentsCorePack Import/Export Tool Data |
| dcpy | Disk Copy Data |
| dcs | QuarkXPress Desktop Color Separation Data |
| dcsdb2 | 3DCS Database |
| dct | Adobe Illustrator Dictionary |
| dct | Concordance Dictionary Database |
| dct | E-Sword v8 Dictionary Data |
| dct5 | Microsoft Word 5 for Mac Dictionary Data |
| dctmp | DC++ Partially Downloaded |
| dctx | E-Sword v9 Dictionary Data |
| dctxc | Microsoft IME Dictionary Compiler File |
| dcv | DriveCrypt Volume |
| dcw | Draft Choice for Windows Drawing |
| dcy | NETSCAN Decay Search Results |
| dd | OMA Download Descriptor |
| dd2 | OMA Download Agent v2 Descriptor |
| ddat | DivX Temporary Video Data |
| ddb | Protel 99SE Design Database |
| ddb | TINA Shape Library Database |
| ddd | Digital Tachograph Data |