| .BMML | Balsamiq Studios, LLC | Udviklerfiler | Balsamiq Mockups Graphics | Balsamiq Mockups | Balsamiq Studios, LLC |
| .BMT | Alpha Software | Udviklerfiler | Alpha Five Image Library | Alpha Five | Alpha Software |
| .BOS | IBM | Udviklerfiler | Build Options Specification File | IBM Rational ClearCase | IBM |
| .BP | Data Access Worldwide | Udviklerfiler | DataFlex Business Process Object | DataFlex | Data Access Worldwide |
| .BPG | Open Source | Udviklerfiler | Better Portable Graphics (BPG) Image | BPG viewer | Open Source |
| .BPL | Autodesk, Inc. | Udviklerfiler | AutoCAD Batch Plot File | Autodesk AutoCAD | Autodesk, Inc. |
| .BPR | Embarcadero Technologies | Udviklerfiler | Borland C++Builder Project File | C++Builder | Embarcadero Technologies |
| .BPT | Corel | Udviklerfiler | CorelDRAW Bitmap Master Data | CorelDRAW Graphics Suite | Corel |
| .BRH | Sheshadrivasu Chandrashekaran | Udviklerfiler | Baraha Document File | Baraha | Baraha Software |
| .BRX | Qualcomm | Udviklerfiler | BREW Application Resource File | Brew MP SDK | Qualcomm |
| .BS2 | Parallax | Udviklerfiler | BASIC Stamp 2 Code File | Microsoft Notepad | Microsoft Corporation |
| .BSC | Microsoft Corporation | Udviklerfiler | Visual Studio Source Browser Information File | Microsoft Visual Studio | Microsoft Corporation |
| .BSH | Open Source | Udviklerfiler | BeanShell Script | Microsoft Notepad | Microsoft Corporation |
| .BSM | Take-Two Interactive | Udviklerfiler | Bioshock Map Data | BioShock | Take-Two Interactive |
| .BTN | Indigo Rose | Udviklerfiler | AutoPlay Media Studio Button File | AutoPlay Media Studio | Indigo Rose |
| .BWR | Open Source | Udviklerfiler | Kermit Beware Bug List | C-Kermit 9.0 | Open Source |
| .CA2 | Embarcadero Technologies | Udviklerfiler | Delphi Install Disk12 File | Delphi (IDE) | Embarcadero Technologies |
| .CA5 | Embarcadero Technologies | Udviklerfiler | Delphi Install Disk11 File | Delphi (IDE) | Embarcadero Technologies |
| .CAP | Microsoft Corporation | Udviklerfiler | Network Monitor Packet Capture Data File | Microsoft Network Monitor | Microsoft Corporation |
| .CAR | Unknown Developer | Udviklerfiler | Car Explorer Data File | Car Explorer | Unknown Developer |
| .CAS | Autodesk, Inc. | Udviklerfiler | Autodesk Cascade License File | AutoCAD Architecture | Autodesk, Inc. |
| .CBA | WinAbility Software | Udviklerfiler | Comic Book ACE Archive | GonVisor | G.A.A. |
| .CBL | IBM | Udviklerfiler | COBOL Source Code File | GNU Compiler Collection (GCC) | GNU Project |
| .CBP | The Code::Blocks team | Udviklerfiler | Code::Blocks Project File | Code::Blocks | The Code::Blocks team |
| .CC | Don Ho | Udviklerfiler | C/C++ Source Code File | MacroMates TextMate | MacroMates |
| .CCC | Open Source | Udviklerfiler | Dev-C++ Code Completion Cache | Dev-C++ | Bloodshed Software |
| .CCN | Clickteam | Udviklerfiler | Compressed Multimedia Fusion File | Multimedia Fusion | Interscape |
| .CCP | Ambiera | Udviklerfiler | CopperCube JavaScript File | CopperCube | Ambiera |
| .CCS | YesSoftware | Udviklerfiler | CodeCharge Studio Project File | CodeCharge Studio | YesSoftware |
| .CD | Microsoft Corporation | Udviklerfiler | Visual Studio Class Diagram | Microsoft Visual Studio | Microsoft Corporation |
| .CDF | Wolfram Research | Udviklerfiler | Computable Document Format File | Wolfram Research CDF Player | Wolfram Research |
| .CDX | Microsoft Corporation | Udviklerfiler | Compound Index File | Microsoft Visual FoxPro | Microsoft Corporation |
| .CDXML | PerkinElmer | Udviklerfiler | ChemDraw XML File | Open Babel | Open Babel development team |
| .CFC | Adobe Systems Incorporated | Udviklerfiler | ColdFusion Component File | Adobe Dreamweaver | Adobe Systems Incorporated |
| .CFG | Unknown Developer | Udviklerfiler | Configuration File | Microsoft Notepad | Microsoft Corporation |
| .CGI | Unknown Developer | Udviklerfiler | Common Gateway Interface Script | Microsoft Notepad | Microsoft Corporation |
| .CGL | Embarcadero Technologies | Udviklerfiler | CodeGuard Error Log File | RAD Studio | Embarcadero Technologies |
| .CH | CA Technologies | Udviklerfiler | Clipper Include File | Clipper | CA Technologies |
| .CHB | Microsoft Corporation | Udviklerfiler | OLE-DB Checkbook File | Unknown Software | Unknown Developer |
| .CI | Microsoft Corporation | Udviklerfiler | Windows Content Indexer Catalog File | Microsoft Windows | Microsoft Corporation |
| .CK | Ge Wang | Udviklerfiler | ChucK Source Code | ChucK | Ge Wang |
| .CKBX | Cricket Technology | Udviklerfiler | Cricket Audio XML Bank Description File | Cricket audio | Cricket Technology |
| .CKM | Bethesda Softworks | Udviklerfiler | Creation Kit Macro | The Elder Scrolls V: Skyrim | Bethesda Softworks |
| .CLA | Oracle Corporation | Udviklerfiler | Java Class Data | Java | Oracle Corporation |
| .CLASS | Oracle Corporation | Udviklerfiler | Java Class File | Eclipse IDE for Java Developers | The Eclipse Foundation |
| .CLJ | Open Source | Udviklerfiler | Clojure Source Code | Clojure | Open Source |
| .CLU | Revolution Software | Udviklerfiler | Broken Sword 2 Dialogue Data | Broken Sword 2 | Revolution Software |
| .CLW | Microsoft Corporation | Udviklerfiler | Visual C++ ClassWizard File | Microsoft Visual C++ | Microsoft Corporation |
| .CMA | Pierre Chambart, Jean-Christophe FILLIATRE and Sylvain Le Gall | Udviklerfiler | Applix Builder File | Camomile (Library File) | Pierre Chambart, Jean-Christophe FILLIATRE and Sylvain Le Gall |
| .CMAKE | Kitware, Inc. | Udviklerfiler | CMake File | CMake | Kitware, Inc. |
| .CNT | Microsoft Corporation | Udviklerfiler | Help Contents File | Microsoft HTML Help Workshop | Microsoft Corporation |
| .COB | IBM | Udviklerfiler | COBOL Source Code File | GNU Compiler Collection (GCC) | GNU Project |
| .COD | Unknown Developer | Udviklerfiler | Compiled Source Code | Microsoft Visual Studio | Microsoft Corporation |
| .COLA | Melvin Smith | Udviklerfiler | Cola Source Code File | COLA | Melvin Smith |
| .CONFIG | Unknown Developer | Udviklerfiler | Configuration File | Microsoft Notepad | Microsoft Corporation |
| .CP | Apple | Udviklerfiler | Xcode C++ Source File | Apple Xcode | Apple |
| .CPJ | NVIDIA | Udviklerfiler | NVIDIA CUDA Project | CUDA ToolKit | NVIDIA |
| .CPP | Open Source | Udviklerfiler | C++ Source Code File | Microsoft Visual Studio | Microsoft Corporation |
| .CPZ | Terry A. Davis | Udviklerfiler | LoseThos C+ Source File | LoseThos | Terry A. Davis |
| .CR2 | Canon Inc. | Udviklerfiler | Canon Digital Camera Raw Image File | CodedColor PhotoStudio | 1Stein |
| .CR5 | Campbell Scientific | Udviklerfiler | CRBasic Source Code File | CR300-Series Dataloggers | Campbell Scientific |
| .CR7 | Campbell Scientific | Udviklerfiler | CRBasic Source Code File | CR300-Series Dataloggers | Campbell Scientific |
| .CS | Microsoft Corporation | Udviklerfiler | C# Source Code File | Notepad++ | Don Ho |
| .CSB | Corel | Udviklerfiler | Corel PHOTO-PAINT Script | Corel Photo-Paint | Corel |
| .CSC | Corel | Udviklerfiler | Corel Script File | Corel Photo-Paint | Corel |
| .CSHRC | The Open Group | Udviklerfiler | Unix Command Data | GNU Emacs | GNU Project |
| .CSI | ContentServ | Udviklerfiler | ContentServ Include File | ContentServ CS EMMS Suite | ContentServ |
| .CSIG | Open Source | Udviklerfiler | SCons Content Signature | SCons | Open Source |
| .CSN | Adobe Systems Incorporated | Udviklerfiler | Adobe Code Snippet Document | Adobe Dreamweaver | Adobe Systems Incorporated |
| .CSP | RadGs Software | Udviklerfiler | Concept Server Page | Mozilla Firefox | Mozilla |
| .CSPROJ | Microsoft Corporation | Udviklerfiler | Visual Studio C# Project | Microsoft Visual Studio | Microsoft Corporation |
| .CST | Smith Micro Software | Udviklerfiler | Manga Studio Story File | Manga Studio | Smith Micro Software |
| .CSX | Microsoft Corporation | Udviklerfiler | Visual C# Script | Notepad++ | Don Ho |
| .CTC | Microsoft Corporation | Udviklerfiler | Visual Studio Command Table Configuration | Microsoft Visual Studio | Microsoft Corporation |
| .CTL | Open Source | Udviklerfiler | StepMania SMZIP Package Description File | StepMania | Open Source |
| .CTP | Cake Software Foundation | Udviklerfiler | CakePHP Template | Adobe Dreamweaver | Adobe Systems Incorporated |
| .CTX | Microsoft Corporation | Udviklerfiler | Visual Basic Control Binary File | Microsoft Visual Studio | Microsoft Corporation |
| .CU | NVIDIA | Udviklerfiler | CUDA Source Code File | Microsoft Notepad | Microsoft Corporation |
| .CUF | Borland | Udviklerfiler | Turbo C Utilities Form Definition | Turbo C | Borland |
| .CV4 | Microsoft Corporation | Udviklerfiler | Microsoft CodeView Graphics Data | CodeView | Microsoft Corporation |
| .CWL | Open Source | Udviklerfiler | TeXstudio Completion Word List | TeXstudio | Open Source |
| .CX | OrbiTech Ltd. | Udviklerfiler | CodeMapper Script | CodeMapper | OrbiTech Ltd. |
| .CXE | Sublime HQ Pty Ltd | Udviklerfiler | Common XML Envelope Data | Microsoft Notepad | Microsoft Corporation |
| .CXP | Omron Corporation | Udviklerfiler | CX-Programmer Project File | OMRON CX-One | Omron Corporation |
| .CXT | Omron Corporation | Udviklerfiler | CX-Programmer Project Text File | OMRON CX-One | Omron Corporation |
| .CXX | Embarcadero Technologies | Udviklerfiler | C++ Main Source Code File Format | Eclipse CDT | The Eclipse Foundation |
| .CYA | Peter Güntert | Udviklerfiler | Cyana Macro | Cyana | Peter Güntert |
| .C__ | Open Source | Udviklerfiler | C++ Source Code File | Microsoft Visual Studio | Microsoft Corporation |
| .D2J | Unknown Developer | Udviklerfiler | D2jsp Script File | Unknown Software | Unknown Developer |
| .D4 | Open Source | Udviklerfiler | Dataphor Source File | Dataphor | Open Source |
| .DART | Google | Udviklerfiler | Dart Source Code File | DART | DARTECH |
| .DBA | PDC (Prolog Development Center) | Udviklerfiler | Turbo Prolog Database | Visual Prolog | PDC (Prolog Development Center) |
| .DBML | Microsoft Corporation | Udviklerfiler | Visual Studio OR Design File | Microsoft Visual Studio | Microsoft Corporation |
| .DBP | Microsoft Corporation | Udviklerfiler | Microsoft Visual Studio Visual C++ Database Project | Microsoft Notepad | Microsoft Corporation |
| .DBPRO | The Game Creators | Udviklerfiler | DarkBASIC Professional Project File | The Game Creators DarkBASIC Pro | The Game Creators |
| .DCF | Sony Mobile Communications | Udviklerfiler | DRM Content Format File | DRM Packager | Sony Mobile Communications |
| .DCP | Embarcadero Technologies | Udviklerfiler | Delphi Compiled Package | Delphi (IDE) | Embarcadero Technologies |
| .DCU | Embarcadero Technologies | Udviklerfiler | Delphi Compiled Unit | Delphi (IDE) | Embarcadero Technologies |
| .DCUIL | Embarcadero Technologies | Udviklerfiler | Delphi .NET Compiled Unit File | Delphi (IDE) | Embarcadero Technologies |
| .DCURL | SCSK Corporation | Udviklerfiler | Curl - Detached Applet File | Curl | SCSK Corporation |
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