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