File extensions start with character 'C'
| File Type | Category | File Format | |
|---|---|---|---|
| .c | Development Files | C/C++ Source Code File | |
| .c00 | Archive Files | WinAce Split Archive File | |
| .c01 | Archive Files | WinAce Split Archive Part 1 File | |
| .c01 | Audio Files | Typhoon Wave Audio File | |
| .c2d | Disk Image Files | WinOnCD Disc Image | |
| .c32 | Archive Files | Syslinux COM32 Module | |
| .c4d | 4D File Format Files | Cinema 4D Model File | |
| .cab | Windows Cabinet Files | Windows Cabinet File | |
| .cache | Multiple Use Files | Cache File | |
| .caf | Audio Files | Core Audio File | |
| .capx | Development Files | Construct Compressed Project File | |
| .car | Archive Files | Car Explorer Data File | |
| .cas | Multiple Use Files | Autodesk Cascade License File | |
| .cat | Auto CAD Files | Windows Catalog File | |
| .catpart | CAD Files | CATIA V5 Part File | |
| .cav | Data Files | Comodo Virus Definitions File | |
| .cba | Basic Files | Comic Book ACE Archive | |
| .cbr | Comic Book Archive Files | Comic Book RAR Archive | |
| .cbz | Comic Book Archive Files | Comic Book Zip Archive | |
| .cca | Data Files | Multimedia Fusion File | |
| .ccd | Description Files | CloneCD Disc Image | |
| .ccip | Protocol Files | Curse Client Install Package | |
| .ccp | Data Files | RIB Import Converter Profile | |
| .ccr | Data Files | ASTM Continuity of Care Record | |
| .cct | Database Files | Director Protected Cast Resource | |
| .cda | Audio Files | CD Audio Track Shortcut | |
| .cdb | Database Files | Symbian Phonebook Database | |
| .cdd | Vector Graphics Files | ConceptDraw PRO Document | |
| .cdda | Audio Files | CD Digital Audio File | |
| .cdf | Page Layout Files | Computable Document Format File | |
| .cdf-ms | Multiple Use Files | ClickOnce Compiled Manifest File | |
| .cdmz | Vector Graphics Files | Compressed ConceptDraw MINDMAP Document | |
| .cdp | Report Files | Trainz Simulator Content Dispatcher Pack | |
| .cdpx | Data Files | ConceptDraw PROJECT XML File | |
| .cdpz | Data Files | ConceptDraw PROJECT Document | |
| .cdr | Vector Graphics Files | CorelDRAW Image File | |
| .cdt | Configuration Files | CorelDRAW Image Template | |
| .cdw | CAD Files | KOMPAS Document | |
| .cdx | CorelDRAW Files | Compound Index File | |
| .cdxml | XML Files | ChemDraw XML File | |
| .cel | Adobe Files | Affymetrix Probe Results File | |
| .celtx | Project Files | Celtx Project File | |
| .cfa | Audio Files | Adobe Conformed Audio File | |
| .cfg | Configuration Files | Configuration File | |
| .cfr | Report Files | Cross Fire Replay File | |
| .cfs | Configuration Files | Compact File Set Archive | |
| .cfxr | Audio Files | Cocoa Sfxr File | |
| .cgf | Data Files | Crytek Geometry Format File | |
| .cgr | CAD Files | CATIA Graphical Representation File | |
| .charset | Text Files | Character Set | |
| .chg | System Files | Windows Net Logon File | |
| .chk | Multiple Use Files | Saved File Fragment | |
| .chm | Microsoft Files | Compiled HTML Help File | |
| .chn | Data Files | Ethnograph Data | |
| .chord | Text Files | Song Chords File | |
| .cidb | Audio Files | iTunes CD Information File | |
| .civ5save | Game Files | Civilization 5 Saved Gae | |
| .ckp | Database Files | SQL Server Checkpoint File | |
| .ckt | Data Files | CircuitMaker File | |
| .cl2 | Data Files | HY-TEK Meet Results File | |
| .cl4 | Data Files | Easy CD Creator 4 Project File | |
| .class | Development Files | Java Class File | |
| .clb | System Files | COM+ Catalog File | |
| .cleo | Mod Files | CLEO Grand Theft Auto Mod File | |
| .clg | Configuration Files | Windows Catalog File | |
| .clix | Data Files | CLIX Command File | |
| .clm | Data Files | MagicJack Call Log File | |
| .clp | Data Files | Windows Clipboard File | |
| .clr | Multiple Use Files | Flash Color Set | |
| .clx | Data Files | Standard Dictionary File | |
| .cmap | Data Files | CmapTools Concept Map File | |
| .cmbl | Data Files | Logger Pro Data File | |
| .cmf | CorelDRAW Files | Cal3D Binary Mesh File | |
| .cmf | Audio Files | Creative Music Format | |
| .cml | Data Files | Chemical Markup Language File | |
| .cmp | Backup Files | HotDocs Clause Component File | |
| .cms | Data Files | Connection Manager Service Profile | |
| .cmx | Vector Graphics Files | Corel Metafile Exchange Image File | |
| .cn1 | Data Files | CNR Modem Initialization Data File | |
| .cna | Data Files | Catena Project File | |
| .cng | Encrypted Files | CryptoNG Encrypted Archive | |
| .cob | Development Files | COBOL Source Code File | |
| .cod | Development Files | Compiled Source Code | |
| .com | Program Execution Files | DOS Command File | |
| .comicdoc | Page Layout Files | Comic Life Document | |
| .component | Apple Files | Mac OS X System Component | |
| .conf | Configuration Files | Unix Configuration File | |
| .config | Development Files | Configuration File | |
| .contact | Microsoft Files | Windows Contact File | |
| .copy | Audio Files | Sony Ericsson Protected Content File | |
| .cos | Configuration Files | Capture One Settings File | |
| .cov | Page Layout Files | Fax Cover Page File | |
| .cpbitmap | Raster Graphics Files | iOS Wallpaper Image | |
| .cpd | CorelDRAW Files | RoboHelp Cache Project Database | |
| .cpf | Data Files | Cognos Project File | |
| .cpgz | Compressed Files | Compressed CPIO Archive | |
| .cpi | Digital Video Files | AVCHD Video Clip Information File | |
| .cpk | Package Files | DTM Test Log File | |
| .cpl | Windows System Files | Windows Control Panel Item | |
| .cpmz | Data Files | Miradi/ConPro Project File | |
| .cpp | Development Files | C++ Source Code File | |
| .cpr | Audio Files | Cubase Project | |
| .cpt | Raster Graphics Files | Corel Photo-Paint Document | |
| .cpt | Audio Files | DTS Compact Audio File | |
| .cptl | Data Files | Adobe Captivate Project Template File | |
| .cptx | Data Files | Adobe Captivate Project File | |
| .cr2 | Camera Photo Files | Canon Raw Image File | |
| .crdownload | Multiple Use Files | Chrome Partially Downloaded File | |
| .crev | Data Files | Adobe Captivate Commentable SWF File | |
| .crtx | Data Files | Office 2007 Chart Template File | |
| .crwl | Text Files | Windows Crawl File | |
| .crx | Google Files | Chrome Extension | |
| .cry | Data Files | CryENGINE Map File | |
| .cs | Development Files | Visual C# Source Code File | |
| .csa | Data Files | PNA Code Calset File | |
| .csd | Page Layout Files | Compact Shared Document | |
| .csh | Multiple Use Files | Photoshop Custom Shapes File | |
| .cso | ISO Files | Compressed ISO Disk Image | |
| .csv | Data Files | Comma Separated Values File | |
| .ct | Printer Files | Cheat Engine Cheat Table | |
| .ctf | Partially Downloaded Files | AVG Update Control File | |
| .ctg | Multiple Use Files | Canon Digital Camera Catalog File | |
| .ctl | Development Files | Visual Basic UserControl Object File | |
| .ctm | Data Files | CrazyTalk Model File | |
| .ctt | Data Files | Messenger Contact List | |
| .ctv | Data Files | Citavi Project | |
| .ctv3 | Data Files | Citavi 3 Project File | |
| .ctx | Microsoft Files | Valve ICE Encoded Script | |
| .cub | Data Files | Analysis Services Cube File | |
| .cue | Description Files | Cue Sheet File | |
| .cur | Windows System Files | Windows Cursor | |
| .cursorfx | Data Files | CursorFX Theme File | |
| .curxptheme | Theme Files | CursorXP Theme File | |
| .cva | Configuration Files | HP Systems Software Manager Information File | |
| .cvd | Data Files | ClamAV Virus Definitions File | |
| .cvn | Data Files | CineVision Encoding Session | |
| .cwk | Data Files | ClarisWorks Document | |
| .cwp | Audio Files | Cakewalk SONAR Project | |
| .cws | Text Files | Claris Works Template | |
| .cwz | Data Files | Circuit Wizard File | |
| .cxt | Adobe Files | Director Protected Cast File | |
| .cyi | Text Files | Clustify Input File | |
| .cyo | Data Files | Clustify Output File |