| cys | Cytoscape Session File |
| cyt | Crocodile Technology Simulation Data |
| cz | Czech Language Related Text |
| czp | ClozePro Archive |
| czr | Everest Advanced Report |
| d01 | MicroSim PCBoard Drill Data |
| d1 | Progress OpenEdge Database |
| d2 | Progress OpenEdge Database |
| d2e | Gaussian Two-Electron Integral Derivative File |
| d3d | Game Maker 3D Data |
| d3p | DigitalPrintLab 3 Data |
| d7d | Dewesoft 7 Data |
| d7s | Dewesoft 7 Setup Data |
| d7t | Dewesoft 7 Sequence Data |
| d83 | GAEB 1990 Data File |
| da0 | Windows Registry Backup |
| da2 | HammerTap DeepAnalysis Save |
| dab | OrangeCD Database |
| daconnections | RemObjects Data Abstract Connections |
| dacpac | SQL Server Data Tier Application Package |
| dadiagrams | RemObjects Data Abstract Data Diagrams |
| daf | Digital Anchor Data |
| dak | Debian Archive Kit Data |
| dal | Download Accelerator Plus List |
| dam | DeltaMaster Analysis Model |
| dan | D-MAS Analysis Data |
| daq | Data Acquisition Toolbox File |
| das | DeltaMaster Analysis Session Data |
| daschema | RemObjects Data Abstract Schema |
| dash | Dashlane Profile |
