| .CATDRAWIN | Unknown Developer | Arquivos miscelâneas | Unknown File Type | Unknown Software | Unknown Developer |
| .CATMATERIA | Unknown Developer | Arquivos miscelâneas | Uncommon File Extension | Unknown Software | Unknown Developer |
| .CB3 | Open Source | Arquivos miscelâneas | CliBench Mk III SMP File | CliBench mk III smp 0.7.17 | Open Source |
| .CBIN | Unknown Developer | Arquivos miscelâneas | CACTVS Chemical Binary File | Unknown Software | Unknown Developer |
| .CBN | j2 Global, Inc. | Arquivos miscelâneas | PaperMaster Cabinet File | PaperMaster Pro | j2 Global, Inc. |
| .CBT | Various Developers | Arquivos miscelâneas | Comic Book TAR File | Smith Micro StuffIt Deluxe | Smith Micro Software |
| .CBX | IBM | Arquivos miscelâneas | Rational XDE Collaboration Data File | Rational XDE | IBM |
| .CCE | Broderbund | Arquivos miscelâneas | Calendar Creator 2 Event File | Calendar Creator | Broderbund |
| .CCH | Microsoft Corporation | Arquivos miscelâneas | .NET Security Resolution Cache File | Microsoft .NET Framework | Microsoft Corporation |
| .CCL | Open Source | Arquivos miscelâneas | CCTools Levelset Data | CCTools | Open Source |
| .CDAT | Microsoft Corporation | Arquivos miscelâneas | Internet Security And Acceleration (ISA) Server Cache File | Microsoft Internet Security and Acceleration (ISA) | Microsoft Corporation |
| .CDEV | Apple | Arquivos miscelâneas | Macintosh II Control Panel File | macOS | Apple |
| .CDEVSAMPLE | Unknown Developer | Arquivos miscelâneas | Uncommon File Extension | Unknown Software | Unknown Developer |
| .CDF-MS | Microsoft Corporation | Arquivos miscelâneas | ClickOnce Compiled Manifest File | Microsoft ClickOnce | Microsoft Corporation |
| .CDMIA | Unknown Developer | Arquivos miscelâneas | Unknown File Type | Unknown Software | Unknown Developer |
| .CDMIC | Unknown Developer | Arquivos miscelâneas | Uncommon File Extension | Unknown Software | Unknown Developer |
| .CDMID | Unknown Developer | Arquivos miscelâneas | Unknown File Type | Unknown Software | Unknown Developer |
| .CDMIO | Unknown Developer | Arquivos miscelâneas | Unknown File Type | Unknown Software | Unknown Developer |
| .CDMIQ | Unknown Developer | Arquivos miscelâneas | Unknown File Type | Unknown Software | Unknown Developer |
| .CDN | Avery Dennison | Arquivos miscelâneas | Click'N Design 3D CD Label File | Click'N Design 3D | Avery Dennison |
| .CDQ | Open Source | Arquivos miscelâneas | Blue Mirror DVD/CD Indexer | Blue Mirror DVD/CD Indexer | Open Source |
| .CDV | Square Box Systems | Arquivos miscelâneas | CatDV Catalog | CatDV | Square Box Systems |
| .CE3 | Broderbund | Arquivos miscelâneas | Calendar Creator 3.x 4.x Event List File | Calendar Creator | Broderbund |
| .CERBER3 | Malwarebytes | Arquivos miscelâneas | Cerber Ransomware Virus File | Kaspersky Anti-Virus | Kaspersky Lab |
| .CES | Unknown Developer | Arquivos miscelâneas | Uncommon File Extension | Unknown Software | Unknown Developer |
| .CFK | Microsoft Corporation | Arquivos miscelâneas | Microsoft Developer Studio Diagram File | Microsoft Visual Studio | Microsoft Corporation |
| .CFL | Corel Corporation | Arquivos miscelâneas | Corel Flow Flow Chart File | Corel WordPerfect | Corel |
| .CFO | Embarcadero Technologies | Arquivos miscelâneas | Turbo C Utilities C Form Object File | Turbo C | Borland |
| .CFS | Apache HTTP Project Management Committee | Arquivos miscelâneas | Lucene Compound Index File | Apache Lucene | Apache Software Foundation |
| .CHANGELOG | Unknown Developer | Arquivos miscelâneas | Project Log Or Record File | Unknown Software | Unknown Developer |
| .CHK | Sophos | Arquivos miscelâneas | InterCheck Checksum Database | Sophos | Sophos |
| .CHW | Microsoft Corporation | Arquivos miscelâneas | Compiled Help Index File | FAR HTML | Helpware |
| .CHXX | Unknown Developer | Arquivos miscelâneas | Unknown File Type | Unknown Software | Unknown Developer |
| .CL | Aha-Soft | Arquivos miscelâneas | Cursor Library | Aha-Soft IconUtils | Aha-Soft |
| .CLKK | Crick Software | Arquivos miscelâneas | Clicker Keyboard | Crick software clicker | Crick Software |
| .CLR | Adobe Systems Incorporated | Arquivos miscelâneas | Animate Color Set | Adobe Animate CC 2017 | Adobe Systems Incorporated |
| .CLS | Leslie Lamport | Arquivos miscelâneas | LaTeX Document Class File | MiKTeX | Christian Schenk |
| .CLV | Yamaha Corporation | Arquivos miscelâneas | Yamaha Cool Voices Data | Yamaha SoundVQ Player | Yamaha Corporation |
| .CMGZ | Unknown Developer | Arquivos miscelâneas | Unknown File Type | Unknown Software | Unknown Developer |
| .CML | Unknown Developer | Arquivos miscelâneas | Chemical Markup Language File | Avogadro | Open Source |
| .CMYK | ImageMagick Studio LLC | Arquivos miscelâneas | Raw Cyan, Magenta, Yellow And Black Bytes Bitmap Image File | ImageMagick | ImageMagick Studio LLC |
| .CO3 | Unknown Developer | Arquivos miscelâneas | Unknown File Type | Unknown Software | Unknown Developer |
| .COCO | Unknown Developer | Arquivos miscelâneas | Unknown Apple II Data File | Unknown Software | Unknown Developer |
| .COF | Microchip Technology Inc. | Arquivos miscelâneas | MPLAB COFF File | MPLAB IDE | Microchip Technology Inc. |
| .COM1476662 | Unknown Developer | Arquivos miscelâneas | Unknown File Type | Unknown Software | Unknown Developer |
| .COMICSCART | Unknown Developer | Arquivos miscelâneas | Unknown File Type | Unknown Software | Unknown Developer |
| .COMMANDLIN | Unknown Developer | Arquivos miscelâneas | Unknown File Type | Unknown Software | Unknown Developer |
| .COMPLICATI | Unknown Developer | Arquivos miscelâneas | Unknown File Type | Unknown Software | Unknown Developer |
| .COMPRESSIO | Unknown Developer | Arquivos miscelâneas | Unknown File Type | Unknown Software | Unknown Developer |
| .CONFIDENTI | Unknown Developer | Arquivos miscelâneas | Unknown File Type | Unknown Software | Unknown Developer |
| .CONFIGDBLI | Unknown Developer | Arquivos miscelâneas | Unknown File Type | Unknown Software | Unknown Developer |
| .CONTENTSON | Unknown Developer | Arquivos miscelâneas | Unknown File Type | Unknown Software | Unknown Developer |
| .CONTROLPAN | Unknown Developer | Arquivos miscelâneas | Unknown File Type | Unknown Software | Unknown Developer |
| .CONVERSION | Unknown Developer | Arquivos miscelâneas | Unknown File Type | Unknown Software | Unknown Developer |
| .CORELPROJE | Unknown Developer | Arquivos miscelâneas | Unknown File Type | Unknown Software | Unknown Developer |
| .CORES | Unknown Developer | Arquivos miscelâneas | Unknown File Type | Unknown Software | Unknown Developer |
| .CORRECTED | Unknown Developer | Arquivos miscelâneas | Unknown File Type | Unknown Software | Unknown Developer |
| .COS2 | Pinnacle Systems Inc. | Arquivos miscelâneas | Pinnacle Studio Cache File | Pinnacle Studio | Corel |
| .CPH_9FA6FA | Unknown Developer | Arquivos miscelâneas | Unknown File Type | Unknown Software | Unknown Developer |
| .CPT | Corel | Arquivos miscelâneas | Corel Photo-Paint Image | Corel Presentations X8 | Corel |
| .CPU | Open Source | Arquivos miscelâneas | Virtual CPU File | CPU Simulation Utility | Open Source |
| .CQ1 | Unknown Developer | Arquivos miscelâneas | Unknown File Type | Unknown Software | Unknown Developer |
| .CRA | Unknown Developer | Arquivos miscelâneas | Advanced Crack File | Unknown Software | Unknown Developer |
| .CRACKZBYMA | Unknown Developer | Arquivos miscelâneas | Unknown File Type | Unknown Software | Unknown Developer |
| .CRC16 | DigiSoft Innovations | Arquivos miscelâneas | An Unknown Apple II File | Golden Orchard | DigiSoft Innovations |
| .CRD | Open Source | Arquivos miscelâneas | Guitar Tabs | Notepad++ | Don Ho |
| .CRDOWNLOAD | Google | Arquivos miscelâneas | Chrome Partially Downloaded File | Google Chrome | Google |
| .CRM | PQ Systems | Arquivos miscelâneas | CHARTrunner Multi Chart Document | CHARTrunner Lean | PQ Systems |
| .CRYPTO | Unknown Developer | Arquivos miscelâneas | Scarab/CryptoKill Ransomware Virus | Unknown Software | Unknown Developer |
| .CRYPTONOTE | Unknown Developer | Arquivos miscelâneas | Unknown File Type | Unknown Software | Unknown Developer |
| .CRYSTALHAM | Unknown Developer | Arquivos miscelâneas | Unknown File Type | Unknown Software | Unknown Developer |
| .CSH | Adobe Systems Incorporated | Arquivos miscelâneas | Photoshop Custom Shapes File | Adobe Photoshop Elements | Adobe Systems Incorporated |
| .CTF | Interscape | Arquivos miscelâneas | WhereIsIt Catalog File | WhereIsIt | Interscape |
| .CTG | Canon Inc. | Arquivos miscelâneas | Canon Digital Camera Catalog File | Unknown Software | Unknown Developer |
| .CUID | Unknown Developer | Arquivos miscelâneas | Baidu.cuid Data | Unknown Software | Unknown Developer |
| .CUL | CursorArts Company | Arquivos miscelâneas | Windows Cursor Library | IconForge | CursorArts Company |
| .CUREXSCHEM | Unknown Developer | Arquivos miscelâneas | Unknown File Type | Unknown Software | Unknown Developer |
| .CUSTOM | Commodore International | Arquivos miscelâneas | Personal Paint File | Amiga Forever | Cloanto Corporation |
| .CVE | Unknown Developer | Arquivos miscelâneas | Unknown File Type | Unknown Software | Unknown Developer |
| .CVF | CPUID | Arquivos miscelâneas | CPU-Z Validation File | CPU-Z | CPUID |
| .CVH | Netmap Software | Arquivos miscelâneas | Proprietary Help File | CVTracker | Netmap Software |
| .CVR | Microsoft Corporation | Arquivos miscelâneas | Microsoft Crash Report File | Microsoft Excel | Microsoft Corporation |
| .CXF | Google | Arquivos miscelâneas | Google Picasa Collage File | Google Picasa | Google |
| .CXS | Open Source | Arquivos miscelâneas | ConciseXML Format File | ConciseXML | Open Source |
| .CX_ | Unknown Developer | Arquivos miscelâneas | Unknown File Type | Unknown Software | Unknown Developer |
| .CY | Unknown Developer | Arquivos miscelâneas | CCS-lib.2 JPEG-v4 File | Unknown Software | Unknown Developer |
| .CYN | Unknown Developer | Arquivos miscelâneas | Cynex Root55 Program Extension File | Unknown Software | Unknown Developer |
| .CZK | Unknown Developer | Arquivos miscelâneas | Unknown File Type | Unknown Software | Unknown Developer |
| .D0 | Unknown Developer | Arquivos miscelâneas | Unknown File Type | Unknown Software | Unknown Developer |
| .D15 | HERE | Arquivos miscelâneas | HERE Maps For Android Map Data Package | HERE Maps | HERE |
| .D82 | Commodore International | Arquivos miscelâneas | Commodore Emulator File | VICE | Open Source |
| .DA | Procedimientos-Uno, S.L. | Arquivos miscelâneas | DAwin Project File | DAwin | Procedimientos-Uno, S.L. |
| .DA! | Unknown Developer | Arquivos miscelâneas | Uncommon File Extension | Unknown Software | Unknown Developer |
| .DA2 | Microsoft Corporation | Arquivos miscelâneas | Windows Dancer File | Windows Media Center | Microsoft Corporation |
| .DA5032 | Unknown Developer | Arquivos miscelâneas | Unknown File Type | Unknown Software | Unknown Developer |
| .DAEMONSCRIPT | Disc Soft Ltd. | Arquivos miscelâneas | Daemon Tools Script | DAEMON Tools | Disc Soft Ltd. |
| .DANGER | Unknown Developer | Arquivos miscelâneas | Unknown File Type | Unknown Software | Unknown Developer |
| .DAP | SpeedBit | Arquivos miscelâneas | Download Accelerator Plus Partial Download | Download Accelerator Plus | SpeedBit |
| .DARBY | Unknown Developer | Arquivos miscelâneas | Uncommon File Extension | Unknown Software | Unknown Developer |
| .DAT | Unknown Developer | Arquivos miscelâneas | Game Data | Dragon UnPACKer | Open Source |
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