| .C16 | Creature Labs | Fichiers de jeu | C16 Creatures 3/Docking Station Image | Creature Labs Creatures | Creature Labs |
| .C4S | RedWolf Design | Fichiers de jeu | Clonk Game Scenario File | Clonk Game | RedWolf Design |
| .C4U | Open Source | Fichiers de jeu | OpenClonk Update System File | OpenClonk | Open Source |
| .C4V | RedWolf Design | Fichiers de jeu | Clonk Game Video File | Clonk Game | RedWolf Design |
| .CAR | Unknown Developer | Fichiers de jeu | Car Explorer Data File | Car Explorer | Unknown Developer |
| .CARD | GameHouse | Fichiers de jeu | Funkiball Adventure Game File | Funkiball Adventure | GameHouse |
| .CBF | Tailwag Software | Fichiers de jeu | Calendar Builder File | Calendar Builder | Tailwag Software |
| .CBH | ChessBase GmbH | Fichiers de jeu | ChessBase Database Header File | ChessBase Reader | ChessBase GmbH |
| .CBS | Pelican Accessories | Fichiers de jeu | Code Breaker PS2 Save File | Mymc | Open Source |
| .CBV | ChessBase GmbH | Fichiers de jeu | ChessBase Database File | ChessBase Reader | ChessBase GmbH |
| .CCH | Microsoft Corporation | Fichiers de jeu | .NET Security Resolution Cache File | Microsoft .NET Framework | Microsoft Corporation |
| .CDP | Trainz portal | Fichiers de jeu | Trainz Simulator Content Dispatcher Pack | N3V Games Trainz Simulator | Trainz portal |
| .CEM | Tilted Mill Entertainment | Fichiers de jeu | Children Of The Nile Model File | Tilted Mill Entertainment Children of the Nile | Tilted Mill Entertainment |
| .CETRAINER | Open Source | Fichiers de jeu | Cheat Engine Trainer File | Cheat Engine | Open Source |
| .CFR | Z8Games | Fichiers de jeu | Cross Fire Replay File | Crossfire | Z8Games |
| .CGF | Ubisoft | Fichiers de jeu | Crytek Geometry Format File | CRYENGINE | Crytek |
| .CGG | Electronic Arts | Fichiers de jeu | Renegade Paintball Audio Data | Renegade | Electronic Arts |
| .CGO | PopTop Software Inc. | Fichiers de jeu | Railroad Tycoon 3 Car Properties File | Railroad Tycoon 3 | PopTop Software Inc. |
| .CGT | Gold Parsing System Team | Fichiers de jeu | Gold Parsing System Compiled Grammar Table File | GOLD | Gold Parsing System Team |
| .CGZ | Wouter van Oortmerssen | Fichiers de jeu | Cube Map File | Cube | Wouter van Oortmerssen |
| .CHAR | Nintendo | Fichiers de jeu | Nintendo DS Character Tile Data File | Tinke | Pleonex |
| .CHD | Open Source | Fichiers de jeu | MAME Hard Disk Image | MAME | Open Source |
| .CHESSTITANSSAVE-MS | Microsoft Corporation | Fichiers de jeu | Chess Titans Saved Game | Microsoft Windows | Microsoft Corporation |
| .CHK | Sophos | Fichiers de jeu | InterCheck Checksum Database | Sophos | Sophos |
| .CHM | Microsoft Corporation | Fichiers de jeu | Compiled HTML Help File | Mozilla Firefox | Mozilla |
| .CHT | Nintendo | Fichiers de jeu | SNES Cheat File | ZSNES | Nintendo |
| .CHUZZLEDELUXESAVEDGAME | Yahoo! | Fichiers de jeu | Chuzzle Deluxe Saved Game | Chuzzle | PopCap Games |
| .CIA | Nintendo | Fichiers de jeu | CTR Importable Archive | Ctrtool | Interscape |
| .CIV | Activision | Fichiers de jeu | Empire Earth Custom Civilization Information File | Empire Earth | Sierra Entertainment |
| .CIV4SAVEDGAME | Firaxis Games | Fichiers de jeu | Civilization IV Save Game File | Civilization | Take-Two Interactive |
| .CIV4WORLDBUILDERSAVE | Firaxis Games | Fichiers de jeu | Civilization IV World Builder Save File | Civilization lV | Firaxis Games |
| .CK2 | id Software | Fichiers de jeu | Commander Keen 2 Game Data | TED5 | id Software |
| .CLB | Microsoft Corporation | Fichiers de jeu | COM+ Catalog File | Microsoft COM+ | Microsoft Corporation |
| .CLI | Rockstar Games | Fichiers de jeu | Grand Theft Auto Clip Data File | Grand Theft Auto IV | Rockstar Games |
| .CLIP | CELSYS | Fichiers de jeu | Clip Studio Format File | CELSYS Clip Studio Paint Pro | CELSYS |
| .CLOG | SpreadMaster | Fichiers de jeu | SpreadMaster Client Log File | Unknown Software | Unknown Developer |
| .CLT | Clarity Legal | Fichiers de jeu | Clarity Legal Transcript File | Clarity Legal Viewer | Clarity Legal |
| .CLU | Revolution Software | Fichiers de jeu | Broken Sword 2 Dialogue Data | Broken Sword 2 | Revolution Software |
| .CM | Rockstar Games | Fichiers de jeu | CLEO Custom Mission | Sanny Builder | Open Source |
| .CMD | Microsoft Corporation | Fichiers de jeu | Windows Command File | Microsoft Notepad | Microsoft Corporation |
| .CME | Viva Media, LLC | Fichiers de jeu | Crazy Machines Experiment File | Crazy Machines | FAKT Software |
| .CMG | Ubisoft | Fichiers de jeu | ChessMaster Saved Game | ChessMaster | Ubisoft Blue Byte |
| .CML | Unknown Developer | Fichiers de jeu | Chemical Markup Language File | Avogadro | Open Source |
| .CMP | Microsoft Corporation | Fichiers de jeu | Windows Connection Manager Profile | Microsoft Windows Server 2016 | Microsoft Corporation |
| .CNS | Elecbyte | Fichiers de jeu | M.U.G.E.N. Character States File | Elecbyte M.U.G.E.N | Elecbyte |
| .CNT | Microsoft Corporation | Fichiers de jeu | Help Contents File | Microsoft HTML Help Workshop | Microsoft Corporation |
| .COF | Microchip Technology Inc. | Fichiers de jeu | MPLAB COFF File | MPLAB IDE | Microchip Technology Inc. |
| .COK | Eidos Interactive | Fichiers de jeu | Carmageddon Patch File | Carmageddon TDR 2000 | Torus Games |
| .COL | Open Source | Fichiers de jeu | Bibexcel File | BibExcel | Open Source |
| .COMFYCAKESSAVE-MS | Microsoft Corporation | Fichiers de jeu | Comfy Cakes Saved Game File | Comfy Cakes | Microsoft Corporation |
| .COS | Phase One | Fichiers de jeu | Capture One Settings File | Capture One | Phase One |
| .CPK | CRI Middleware | Fichiers de jeu | CRI Middleware Package | CRI Packed File Maker | CRI Middleware |
| .CPN | Microsoft Corporation | Fichiers de jeu | Age Of Mythology Campaign File | Microsoft Age of Empires | Ensemble Studios |
| .CPR | Steinberg | Fichiers de jeu | Cubase Project | Steinberg Cubase | Steinberg |
| .CPS | Interscape | Fichiers de jeu | The Powder Toy Save File | The Powder Toy | Interscape |
| .CPX | Oracle Corporation | Fichiers de jeu | Oracle ADF Binding Context File | Oracle JDeveloper | Oracle Corporation |
| .CRE | BioWare | Fichiers de jeu | Infinity Engine Creature Data | Baldur's Gate | BioWare |
| .CRF | Open Source | Fichiers de jeu | Cal3D Binary Materials File | Cal3DViewer | Open Source |
| .CRP | dBase, LLC | Fichiers de jeu | dBASE IV Encrypted Database | dBase | dBase, LLC |
| .CRS | Open Source | Fichiers de jeu | StepMania Course File | StepMania | Open Source |
| .CRYSISJMSF | Crytek | Fichiers de jeu | Crysis Saved Game | Crysis | Crytek |
| .CS | Microsoft Corporation | Fichiers de jeu | C# Source Code File | Notepad++ | Don Ho |
| .CSB | Corel | Fichiers de jeu | Corel PHOTO-PAINT Script | Corel Photo-Paint | Corel |
| .CSC | Corel | Fichiers de jeu | Corel Script File | Corel Photo-Paint | Corel |
| .CSD | Valve | Fichiers de jeu | Steam Game Data Backup File | Steam | Valve |
| .CT | Unknown Developer | Fichiers de jeu | Cheat Engine Cheat Table | Cheat Engine | Open Source |
| .CTM | LucasArts Entertainment Company, LLC | Fichiers de jeu | Star Wars Republic Commando Map File | Star Wars Republic Commando | LucasArts Entertainment Company, LLC |
| .CTP | Cake Software Foundation | Fichiers de jeu | CakePHP Template | Adobe Dreamweaver | Adobe Systems Incorporated |
| .CTX | Microsoft Corporation | Fichiers de jeu | Visual Basic Control Binary File | Microsoft Visual Studio | Microsoft Corporation |
| .CTY | EA Maxis | Fichiers de jeu | SimCity City File | Maxis SimCity 2000 | EA Maxis |
| .CUP | Naviter | Fichiers de jeu | Naviter SeeYou Waypoint File | SeeYou | Naviter |
| .CVM | Vanillaware Ltd. | Fichiers de jeu | Odin Sphere Data | Odin Sphere | Vanillaware Ltd. |
| .CW3 | Apple | Fichiers de jeu | ClarisWorks Document | Apple Pages | Apple |
| .CWD | Alexander S. Meshcheryakov | Fichiers de jeu | QNonograms Puzzle File | QNonograms | Alexander S. Meshcheryakov |
| .CWG | Epic Games | Fichiers de jeu | Castle Of The Winds Data | Castle of the Winds | Epic Games |
| .CWZ | New Wave Concepts | Fichiers de jeu | Circuit Wizard File | Circuit Wizard | New Wave Concepts |
| .CYR | Crytek | Fichiers de jeu | Crysis Game Level | Crysis | Crytek |
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