| cp2 | Compel v2 Presentation |
| cpdt | Adobe Captivate Design Template |
| cpe | Microsoft Fax Cover Page File |
| cph | Corel Print House Document |
| cpl | Corel Colour Palette |
| cpo | Corel Print House Document |
| cpr | Corel Presents Presentation |
| cpx | Corel ArtShow 5 Document |
| cpy | eCopy Document |
| cqp | CompuQuilter Pattern |
| crb | BigOven Core Recipe Box |
| crd | Guitar Chord File |
| crf | CHARTrunner Chart Document |
| crm | CHARTrunner Multi Chart Document |
| crtr | MultiAd Creator Pro Document |
| crv | VCarve Pro Design |
| crv3d | Vectric Aspire Document |
| csd | Compact Shared Document |
| cse | Cardinal Studio Template File |
| csf | Informative Graphics Content Sealed Format Document |
| csg | OpenSCAD Constructive Solid Geometry Model |
| css | Cascading Style Sheets |
| cst | Adobe Director Cast |
| csv | Comma-Separated Values |
| ct2 | CTRAN/W Graphical Layout |
| ctb | Color-dependent Plot Style Table |
| cte | Classical Text Editor Document |
| ctex | Chinese TeX Document |
| ctf | WhereIsIt Catalog File |
| ctg | WhereIsIt Catalog Group File |
| ctm | WhereIsIt Template File |
| ctp | CardExchange 7 Card Template |
| ctx | Creativyst Table eXchange Document |
| cvw | Actuate Analytics Cube Report |
| cvw | CaseView Document |