| cdb | Sybase PowerDesigner Conceptual Data Model Backup |
| cdbcmsg | CIM Database CMSG Data |
| cdcom | Circuit Diagram Compiled Components File |
| cde | CADKEY Dynamic Extension |
| cded | Canadian Digital Elevation Data |
| cdf | ANDI/netCDF Chromatography Data |
| cdf | Affymetrix Chip Description File |
| cdf | netCDF Data |
| cdf | ECMG Content Definition File |
| cdf-ms | ClickOnce Compiled Manifest |
| cdfx | Cindex Data |
| cdic | ConlangDictionary Data |
| cdl | Common Data Form Language File |
| cdm | Sybase PowerDesigner Conceptual Data Model |
| cdmp | WCS Device Model Profile |
| cdoc | DigiDoc Crypted Document |
| cdrx | Bosch Crash Data Retrieval Data |
| cdss | CorelDRAW Style Sheet |
| cdv | Broken Cross Disk Manager v1 Database |
| cdv | CatDV Catalog |
| cdws | CorelDraw X7 Workspace |
| cdx | dBASE Compound Index |
| cdx3 | Cochlear Data Exchange File |
| cea | Compressed ENVIS Archive |
| ced | EEGLAB Channel Data |
| cee | CN3 Compressed Extended Ephemeris Data |
| cef | QPEACE Cluster Exchange Format Data |
| ceh | QPEACE Cluster Exchange Format Header |
| cei | CRiSP Harvest Settings Data |
| ceimg | CeRegEditor Registry Image |
| cel | Affymetrix Probe Array Results File |
| cell | CASTEP Cell Input Data |
| celx | Celestia Script File |
| cen | CEN EN 13032 Photometric Data |
| cert | Netscape Certificate Index |