| dbw | Alfrin Pedigree Database |
| dbwal | iOS CalDAV Temporary Sync Data |
| dbx | Microsoft Outlook Express Folder Database |
| dby | Dolby CP650 Data |
| dbz | DB Zipper Archive |
| dc4 | ViaThinkSoft DeCoder 4 File |
| dca | Visual Basic Active Designer Cache |
| dcb | DAZ Studio Custom Brick |
| dcb | Concordance Database |
| dcd | DisCryptor Encrypted Database |
| dcd | CHARMM DCD File |
| dcf | OMA DRM Content Format |
| dcf | DOpus Command File |
| 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 |
| dct | Adobe Illustrator Dictionary |
| dct | E-Sword v8 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 |
| ddb | Protel 99SE Design Database |
| ddb | TINA Shape Library Database |
| ddd | Digital Tachograph Data |
| ddd | Verity Server Data |
| dde | ABBYY Lingvo Dictionary Error Log |