| crl | Certificate Revocation List |
| crld | Clicker Crick Resource Library Data |
| crm | WRAP Conditional Reliability Modeling Data |
| crmlog | Microsoft Windows COM+ CRM Log |
| cro | CropWat Data |
| cro | AquaCrop Crop Data |
| crossdb | MixVibes Cross DJ Collection Data |
| crpt | Cryptosaurus Encrypted File |
| crq | Blackboard Course Requests |
| crr | Cgatools CRR File |
| crs | CompuTrainer Chart Screen |
| crs | Document Conversion Resource |
| crtx | Microsoft Excel 2007 Custom Chart Template |
| crv | Programmable Curves Data |
| crv | ANSYS TurboGrid Curve File |
| crw | CHARTrunner Workspace |
| crwl | Windows Search Crawl Data |
| crypt | WhatsApp Stored Messages |
| crypt10 | WhatsApp Stored Messages |
| crypt11 | WhatsApp Stored Messages |
| crypt12 | WhatsApp Stored Messages |
| crypt5 | WhatsApp Stored Messages |
| crypt6 | WhatsApp Stored Messages |
| crypt7 | WhatsApp Stored Messages |
| crypt8 | WhatsApp Stored Messages |
| crypt9 | WhatsApp Stored Messages |
| crypted | Ashampoo WinOptimizer Encrypted Data |
| cryptra | Cryptra One Time Pad Encrypted File |
| crz | Poser Compressed Character |
| cs | ClearSilver Template File |
| cs | Adobe Encore Color Set |
| cs3 | Casio WK-1800 Song Sequencer Data |
| csa | Cadstar Schematic Design |
| csaplan | SPSS Complex Sample Analysis Plan |
| csar | CARIS Spatial Archive |