| .C4D | MAXON Computer | 3D Image Files | Cinema 4D Model File | Adobe After Effects | Adobe Systems Incorporated |
| .CACHE | Various Developers | Uncommon Files | Cache File | Adobe Photoshop | Adobe Systems Incorporated |
| .CAL | Newera Software Technology, Inc. | Raster Image Files | CALS Raster File | Adobe Photoshop | Adobe Systems Incorporated |
| .CALS | Newera Software Technology, Inc. | Raster Image Files | CALS Raster File | Adobe Photoshop | Adobe Systems Incorporated |
| .CATPRODUCT | Dassault Systèmes | CAD Files | CATIA V5 Assembly File | Adobe Acrobat DC | Adobe Systems Incorporated |
| .CCT | Adobe Systems Incorporated | Data Files | Director Protected Cast Resource | Adobe Director | Adobe Systems Incorporated |
| .CDR | Corel | Vector Image Files | CorelDRAW Vector Image File | Adobe Illustrator CC | Adobe Systems Incorporated |
| .CEF | Richard Stott | Data Files | Class Action Gradebook Elementary File | Adobe Illustrator CC | Adobe Systems Incorporated |
| .CEL | Affymetrix | Data Files | Affymetrix Probe Results File | Adobe Audition | Adobe Systems Incorporated |
| .CER | Microsoft Corporation | Web Files | Internet Security Certificate | Adobe Acrobat DC | Adobe Systems Incorporated |
| .CFA | Frontline | Data Files | ComProbe Analyzer Capture File | Adobe Premiere Pro CC | Adobe Systems Incorporated |
| .CFC | Adobe Systems Incorporated | Developer Files | ColdFusion Component File | Adobe Dreamweaver | Adobe Systems Incorporated |
| .CFG | Unknown Developer | Developer Files | Configuration File | Brackets | Adobe Systems Incorporated |
| .CFM | Adobe Systems Incorporated | Web Files | ColdFusion Markup File | Adobe Dreamweaver | Adobe Systems Incorporated |
| .CGM | Unknown Developer | Vector Image Files | Computer Graphics Metafile | Adobe Illustrator CC | Adobe Systems Incorporated |
| .CGR | Dassault Systèmes | CAD Files | CATIA Graphical Representation File | Adobe Acrobat DC | Adobe Systems Incorporated |
| .CHA | Snak Software | Web Files | IRC Chat Configuration File | Adobe Photoshop CC | Adobe Systems Incorporated |
| .CIN | Kodak | Raster Image Files | Kodak Cineon Bitmap File | Adobe SpeedGrade | Adobe Systems Incorporated |
| .CLR | Adobe Systems Incorporated | Uncommon Files | Animate Color Set | Adobe Animate CC 2017 | Adobe Systems Incorporated |
| .CLX | IBM | Data Files | Rational XDE | Adobe Illustrator CC | Adobe Systems Incorporated |
| .CMX | Corel | Vector Image Files | Corel Metafile Exchange Image File | Adobe Illustrator CC | Adobe Systems Incorporated |
| .COLLECTION | Adobe Systems Incorporated | Data Files | Adobe Bridge Collection File | Adobe Bridge CC | Adobe Systems Incorporated |
| .CONFIG | Unknown Developer | Developer Files | Configuration File | Brackets | Adobe Systems Incorporated |
| .CP | Apple | Developer Files | Xcode C++ Source File | Adobe Captivate | Adobe Systems Incorporated |
| .CPD | Adobe Systems Incorporated | Data Files | RoboHelp Cache Project Database | Adobe RoboHelp | Adobe Systems Incorporated |
| .CPI | Sony | Video Files | AVCHD Video Clip Information | Adobe Premiere Pro CC | Adobe Systems Incorporated |
| .CPR | Steinberg | Audio Files | Cubase Project | Adobe Captivate | Adobe Systems Incorporated |
| .CPS | Interscape | Game Files | The Powder Toy Save File | Adobe Captivate | Adobe Systems Incorporated |
| .CR2 | Canon Inc. | Camera Raw Files | Canon Digital Camera Raw Image File | Adobe Photoshop Elements | Adobe Systems Incorporated |
| .CRW | Canon Inc. | Camera Raw Files | Canon Raw CIFF Image File | Adobe Photoshop Elements | Adobe Systems Incorporated |
| .CS | Microsoft Corporation | Developer Files | C# Source Code File | Adobe Dreamweaver | Adobe Systems Incorporated |
| .CSF | Intergraph Corporation | GIS Files | GeoMedia Coordinate System File | Adobe Illustrator CC | Adobe Systems Incorporated |
| .CSH | Adobe Systems Incorporated | Uncommon Files | Photoshop Custom Shapes File | Adobe Photoshop Elements | Adobe Systems Incorporated |
| .CSN | Adobe Systems Incorporated | Developer Files | Adobe Code Snippet Document | Adobe Dreamweaver | Adobe Systems Incorporated |
| .CST | Smith Micro Software | Page Layout Files | Manga Studio Story File | Adobe Director | Adobe Systems Incorporated |
| .CT | Unknown Developer | Game Files | Cheat Engine Cheat Table | Adobe Photoshop | Adobe Systems Incorporated |
| .CTP | Cake Software Foundation | Developer Files | CakePHP Template | Adobe Dreamweaver | Adobe Systems Incorporated |
| .CXT | Omron Corporation | Developer Files | CX-Programmer Project Text File | Adobe Director | Adobe Systems Incorporated |
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