| .CAT | Microsoft Corporation | Fichiers graphiques | Windows Catalog File | Microsoft Windows | Microsoft Corporation |
| .CCK | U.S. Department of Energy | Fichiers graphiques | COMcheck Data File | COMcheck | U.S. Department of Energy |
| .CDB | Nokia | Fichiers graphiques | Symbian Phonebook Database | Nokia PC Suite | Nokia |
| .CDC | Autodesk, Inc. | Fichiers graphiques | AutoCAD DesignCenter Preview Cache File | Autodesk AutoCAD | Autodesk, Inc. |
| .CDF | Wolfram Research | Fichiers graphiques | Computable Document Format File | Wolfram Research CDF Player | Wolfram Research |
| .CDU | Pierre-Emmanuel Gougelet | Fichiers graphiques | CDU-Paint Image Format | XnView MP | XnSoft |
| .CDW | ASCON | Fichiers graphiques | KOMPAS Document | ASCON KOMPAS-3D | ASCON |
| .CEG | Unknown Developer | Fichiers graphiques | Tempra Show Bitmap Graphic File | Unknown Software | Unknown Developer |
| .CFT | Walt Disney Animation Studios | Fichiers graphiques | CFast Graphics | XnView MP | XnSoft |
| .CH1 | IBM | Fichiers graphiques | IBM Freelance Graphics Chart File | Lotus Freelance Graphics | IBM |
| .CIF | Corel | Fichiers graphiques | Easy CD Creator Disk Image | IsoBuster | Smart Projects |
| .CIM | CIMEX Corporation | Fichiers graphiques | CimPack Design Drawing | CimPack design drawing | CIMEX Corporation |
| .CKO | Corel | Fichiers graphiques | Image Mask File | Corel KnockOut 2 | Corel |
| .CLO | Pierre-Emmanuel Gougelet | Fichiers graphiques | Cloe Ray-Tracer Image | XnView MP | XnSoft |
| .CLOUD | GOM & Company | Fichiers graphiques | GOM Atos Scanner Data | Rapidform Explorer (Geomagic Verify Viewer) | Rapidform, Inc. |
| .CMK | Creative Wonders | Fichiers graphiques | Card Shop Plus Card File | Card Shop Plus | Creative Wonders |
| .CMP | Microsoft Corporation | Fichiers graphiques | Windows Connection Manager Profile | Microsoft Windows Server 2016 | Microsoft Corporation |
| .CMT | Chinon Group | Fichiers graphiques | Chinon ES-1000 Digital Camera Image Format | Zoner Photo Studio | Zoner Software |
| .COT | Intergraph Corporation | Fichiers graphiques | Intergraph Image File | Intergraph SG&I software | Intergraph Corporation |
| .CP8 | Unknown Developer | Fichiers graphiques | CP8 256 Gray Scale Image | XnView MP | XnSoft |
| .CRF | Open Source | Fichiers graphiques | Cal3D Binary Materials File | Cal3DViewer | Open Source |
| .CS4 | Sinar | Fichiers graphiques | Sinar CaptureShop 4-shot Image File | Sinar CaptureShop | Sinar |
| .CSA | Agilent Technologies | Fichiers graphiques | PNA Code Calset File | PNA Code | Agilent Technologies |
| .CSE | Macropool | Fichiers graphiques | Web Research Document Package | Web Research Professional | Macropool |
| .CSN | Adobe Systems Incorporated | Fichiers graphiques | Adobe Code Snippet Document | Adobe Dreamweaver | Adobe Systems Incorporated |
| .CT2 | Geoslope | Fichiers graphiques | CTRAN/W Graphical Layout File | CTRAN/W | Geoslope |
| .CTM | LucasArts Entertainment Company, LLC | Fichiers graphiques | Star Wars Republic Commando Map File | Star Wars Republic Commando | LucasArts Entertainment Company, LLC |
| .CU1 | Computerinsel GmbH | Fichiers graphiques | Photoline4 Curves Curve File | Photoline | Computerinsel GmbH |
| .CURSOR | Sun Microsystems | Fichiers graphiques | Sun Cursor | SunOS | Sun Microsystems |
| .CWR | SAP | Fichiers graphiques | Crystal Reports Report | Crystal Reports | SAP |
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