| cms | Connection Manager Service Provider Data |
| cn3 | Cn3D Data |
| cn3d | Cn3D Data |
| cnf | Configuration File |
| cnf | Origin Configuration File |
| cns | Client Connection Manager Config |
| cntl | GoCart Control Data |
| con | Configuration File |
| conf | Configuration File |
| config | Configuration File |
| controls | OpenBVE Keyboard Shortcuts |
| copreset | Capture One Preset |
| cos | Capture One Settings |
| costyle | Capture One Style |
| cpf | Curtis Programmer Settings |
| cpff | Cam2Com Capture Properties |
| cpm | Cisco Secure Policy Manager Settings |
| cq | CQUAL Configuration |
| crop | Crick Software Clicker Options |
| crp | CureROM Profile |
| cscfg | Microsoft Azure Service Configuration Schema |
| cscnp | Colasoft Capsa Current Node Group List |
| csd | Casio WK-3000 User Scale Memory |
| csf | Adobe InDesign Color Settings |
| cshrc | C Shell Startup Configuration File |
| cskin | CD Art Display Skin |
| csl | CineStyle Color Lookup Settings |
| ctbodyfitting | CrazyTalk Animator Actor Fitting |
| ctf | AVG Update Control File |
| cui | Autodesk AutoCAD Custom Workspace |
