| .123 | IBM | Ficheiros CAD | Lotus 1-2-3 Spreadsheet | Apache OpenOffice | Apache Software Foundation |
| .2D | Archway Systems | Ficheiros CAD | VersaCAD 2D Drawing File | Archway Systems VersaCAD | Archway Systems |
| .2DR | Cadwork SA | Ficheiros CAD | Cadwork Road File | Cadwork | Cadwork SA |
| .3DC | NNG | Ficheiros CAD | iGO 3D Building Data | iGO Navigation | NNG |
| .A2L | Vector Informatik | Ficheiros CAD | ASAP2 ECU Description File | Hexplorer | Open Source |
| .AC | GNU Operating System | Ficheiros CAD | Autoconf Script | GNU Autoconf | GNU Operating System |
| .ACT | Bell Labs | Ficheiros CAD | ADPCM Compressed Audio File | Unknown Software | Unknown Developer |
| .ADI | Active@ Data Recovery Software | Ficheiros CAD | Active@ Disk Image Backup File | Active@ Disk Image | LSoft Technologies Inc. |
| .ADJ | Microsoft partner network | Ficheiros CAD | LISCAD Adjustment File | LISCAD | Microsoft partner network |
| .ADP | Microsoft Corporation | Ficheiros CAD | Access Project Extension | Microsoft Access | Microsoft Corporation |
| .ADT | Swiftpage, Inc. | Ficheiros CAD | ACT! Document Template | Swiftpage Act | Swiftpage, Inc. |
| .AEC | MAXON Computer | Ficheiros CAD | Cinema 4D After Effects Import Composition File | MAXON Cinema 4D | MAXON Computer |
| .AED | Planit Solutions, Inc. | Ficheiros CAD | Alphacam Wire EDM Drawing | Planit Alphacam | Planit Solutions, Inc. |
| .AEF | Autodesk, Inc. | Ficheiros CAD | ELECTRICAL Designe | Autocad Electrical | Autodesk, Inc. |
| .AFD | Planit Solutions, Inc. | Ficheiros CAD | Alphacam Flame Drawing | Planit Alphacam | Planit Solutions, Inc. |
| .AFP | Garmin | Ficheiros CAD | XMap Flight Plan Statistic File | XMap | Garmin |
| .AFS | Bentley Systems | Ficheiros CAD | STAAD.foundation Project File | Bentley Systems STAAD Foundation Advanced | Bentley Systems |
| .AGZ | BedRock Software Inc. | Ficheiros CAD | AggFlow Aggregate Plant Flow Diagram | AggFlow | BedRock Software Inc. |
| .AIG | MCS Investments, Inc. | Ficheiros CAD | Architecture Drawing | Design Your Own Home Architecture | MCS Investments, Inc. |
| .AMB | Bolide Software | Ficheiros CAD | All My Books Database File | All My Books | Bolide Software |
| .AMD | Planit Solutions, Inc. | Ficheiros CAD | Alphacam 3D Mill/2D Mill Drawing | Planit Alphacam | Planit Solutions, Inc. |
| .AMT | Planit Solutions, Inc. | Ficheiros CAD | Alphacam 3D Mill, 2D Mill Tool | Planit Alphacam | Planit Solutions, Inc. |
| .ANL | Planit Solutions, Inc. | Ficheiros CAD | Alphacam Nest List | Planit Alphacam | Planit Solutions, Inc. |
| .ANS | Open Source | Ficheiros CAD | ANSI Text File | Microsoft Notepad | Microsoft Corporation |
| .ANY | DRail Modelspoor Software | Ficheiros CAD | AnyRail Layout Plan | AnyRail | DRail Modelspoor Software |
| .APJ | The FreeBSD Community | Ficheiros CAD | FreeBSD File | FreeBSD | The FreeBSD Community |
| .APP | Nokia | Ficheiros CAD | Symbian OS Application | Symbian OS | Nokia |
| .ARD | Esko | Ficheiros CAD | ArtiosCAD Workspace File | ArtiosCAD | Esko |
| .ART | Autodesk, Inc. | Ficheiros CAD | ArtCAM Model | ArtCAM | Autodesk, Inc. |
| .ASC | Symantec Corporation | Ficheiros CAD | PGP (Pretty Good Privacy) ASCII Armored File | Mozilla Thunderbird | Mozilla |
| .ASM | Open Source | Ficheiros CAD | Assembly Language Source Code File | Microsoft Notepad | Microsoft Corporation |
| .ASP | Microsoft Corporation | Ficheiros CAD | Active Server Page | Mozilla Firefox | Mozilla |
| .ASY | Linear Technology | Ficheiros CAD | LTspice IV Circuit Diagram File | LTspice | Linear Technology |
| .ATB | AnetSoft | Ficheiros CAD | AnetHelp Tools File | AnetHelpTool | AnetSoft |
| .ATD | Planit Solutions, Inc. | Ficheiros CAD | Alphacam Lathe Drawing | Planit Alphacam | Planit Solutions, Inc. |
| .ATH | Dell Boomi | Ficheiros CAD | Alienware AlienFX Theme File | Microsoft XML Notepad | Microsoft Corporation |
| .ATP | Planit Solutions, Inc. | Ficheiros CAD | Alphacam Lathe Post File | Planit Alphacam | Planit Solutions, Inc. |
| .ATT | Unknown Developer | Ficheiros CAD | Web Form Post Data File | LibreOffice | The Document Foundation |
| .B3D | Blitz Research | Ficheiros CAD | Blitz3D Entity Model File | Irrlicht | Open Source |
| .BCD | Microsoft Corporation | Ficheiros CAD | Windows Boot Configuration Data File | Microsoft Registry Editor | Microsoft Corporation |
| .BCE | Graphisoft | Ficheiros CAD | ArchiCAD File | ARCHICAD | Graphisoft |
| .BD4 | West Point | Ficheiros CAD | West Point Bridge Designer Design File | West Point Bridge Designer | Stephen Ressler |
| .BDC | Babylon Software Ltd. | Ficheiros CAD | Babylon Dictionary File | Babylon | Babylon Software Ltd. |
| .BDL | Parametric Technology Corporation | Ficheiros CAD | CoCreate Bundle File | Adobe Acrobat DC | Adobe Systems Incorporated |
| .BIMX | Graphisoft | Ficheiros CAD | BIM Explorer File | BIMx Desktop Viewer | Graphisoft |
| .BIT | Xilinx, Inc. | Ficheiros CAD | Xilinx Bitstream File | ISE Design Suite | Xilinx, Inc. |
| .BLK | Autodesk, Inc. | Ficheiros CAD | AutoCAD Block Template File | Autodesk AutoCAD Ecscad | Autodesk, Inc. |
| .BMF | IMSI/Design, LLC | Ficheiros CAD | FloorPlan File | IMSI TurboCAD Deluxe | Redway3d and others |
| .BOS | IBM | Ficheiros CAD | Build Options Specification File | IBM Rational ClearCase | IBM |
| .BPM | Simple DirectMedia Layer (SDL) | Ficheiros CAD | Trados AutoSuggest Dictionary File | SDL Trados | SDL Trados |
| .BRC | DAZ 3D | Ficheiros CAD | Bryce Version 2 Scene File | DAZ 3D Bryce | DAZ 3D |
| .BRD | Autodesk, Inc. | Ficheiros CAD | EAGLE Circuit Board File | CadSoft EAGLE | Autodesk, Inc. |
| .BSW | AceCad Software Ltd. | Ficheiros CAD | StruWalker 3D Model File | StruWalker | AceCad Software Ltd. |
| .C18 | Dassault Systèmes | Ficheiros CAD | Dassault Systemes Catia V4 Sequential File | Dassault Systemes CATIA | Dassault Systèmes |
| .C6 | Ashlar-Vellum | Ficheiros CAD | Organic 2D/3D Drafting & 3D Modelling Data | Ashlar-Vellum CAD & 3D Modeling | Ashlar-Vellum |
| .CAE | Dassault Systèmes | Ficheiros CAD | Abaqus CAE Model File | Abaqus/Standard | Dassault Systèmes |
| .CAM | Ucamco | Ficheiros CAD | Gerber CAM Job File | CadSoft EAGLE | Autodesk, Inc. |
| .CAT | Microsoft Corporation | Ficheiros CAD | Windows Catalog File | Microsoft Windows | Microsoft Corporation |
| .CATALOG | Dassault Systèmes | Ficheiros CAD | CATIA Catalog File | CATIA | Dassault Systèmes |
| .CATDRAWING | Dassault Systèmes | Ficheiros CAD | CATIA V5 Drawing | Dassault Systemes CATIA | Dassault Systèmes |
| .CATFCT | Dassault Systèmes | Ficheiros CAD | CATIA CATfct Data File | CATIA | Dassault Systèmes |
| .CATMATERIAL | Dassault Systèmes | Ficheiros CAD | CATIA CATMaterial Data | CATIA | Dassault Systèmes |
| .CATPART | Dassault Systèmes | Ficheiros CAD | CATIA V5 Part File | CATIA | Dassault Systèmes |
| .CATPRODUCT | Dassault Systèmes | Ficheiros CAD | CATIA V5 Assembly File | Autodesk Fusion 360 | Autodesk, Inc. |
| .CDD | CS Odessa | Ficheiros CAD | ConceptDraw PRO Document | ConceptDraw PRO | CS Odessa |
| .CDF | Wolfram Research | Ficheiros CAD | Computable Document Format File | Wolfram Research CDF Player | Wolfram Research |
| .CDL | Kubotek Corporation | Ficheiros CAD | CADKEY Wireframe Design File | CADKEY | Kubotek Corporation |
| .CDW | ASCON | Ficheiros CAD | KOMPAS Document | ASCON KOMPAS-3D | ASCON |
| .CEL | Affymetrix | Ficheiros CAD | Affymetrix Probe Results File | The MathWorks MATLAB | MathWorks |
| .CF2 | The Easy Box Builder Internacional | Ficheiros CAD | Common File Format | The Box Builder Modelmaker | The Easy Box Builder Internacional |
| .CFF | The Easy Box Builder Internacional | Ficheiros CAD | Common File Format | The Box Builder Modelmaker | The Easy Box Builder Internacional |
| .CGR | Dassault Systèmes | Ficheiros CAD | CATIA Graphical Representation File | CATIA | Dassault Systèmes |
| .CIB | DIAL | Ficheiros CAD | DIALux Luminaire Data | ReluxSuite | Relux |
| .CIR | Mentor Graphics | Ficheiros CAD | Supermax ECAD Command Save File | edaBase | edaBase |
| .CKD | Kubotek Corporation | Ficheiros CAD | Kubotek Design Container | Kubotek USA KeyCreator | Kubotek Corporation |
| .CLT | Clarity Legal | Ficheiros CAD | Clarity Legal Transcript File | Clarity Legal Viewer | Clarity Legal |
| .CMP | Microsoft Corporation | Ficheiros CAD | Windows Connection Manager Profile | Microsoft Windows Server 2016 | Microsoft Corporation |
| .CNC | Denford Limited | Ficheiros CAD | CNC Machine Tool Path | QuickCAM Pro | Denford Limited |
| .CND | Melco | Ficheiros CAD | Melco Condensed Embroidery File | Dakota AlphaSizer | Dakota Collectibles |
| .CNI | Center for Comparative NeuroImaging | Ficheiros CAD | CWBench File | CWBench | Center for Comparative NeuroImaging |
| .CO | Ashlar-Vellum | Ficheiros CAD | Cobalt 3D Model File | Cobalt | Ashlar-Vellum |
| .CPA | Zuken | Ficheiros CAD | CADSTAR PCB Archive File | Altium Designer | Altium |
| .CPF | IBM | Ficheiros CAD | Cognos Project File | IBM Cognos Business Intelligence | IBM |
| .CPL | Microsoft Corporation | Ficheiros CAD | Windows Control Panel Item | Microsoft Windows | Microsoft Corporation |
| .CSG | Clifford Wolf | Ficheiros CAD | OpenSCAD Constructive Solid Geometry Model | OpenSCAD | Clifford Wolf |
| .CT3 | Microsoft Corporation | Ficheiros CAD | Microsoft Systems Management Server (SMS) Control File | Microsoft Systems Management Server | Microsoft Corporation |
| .CTX | Microsoft Corporation | Ficheiros CAD | Visual Basic Control Binary File | Microsoft Visual Studio | Microsoft Corporation |
| .CYC | Verlag Frese | Ficheiros CAD | CYCAS Design Project | CYCAS | Verlag Frese |
| .CYP | Chief Architect, Inc. | Ficheiros CAD | Home Designer Pro Project File | Home Designer Pro | Chief Architect, Inc. |
| .CZD | FARO Technologies, Inc. | Ficheiros CAD | CAD Zone Drawing | The Crash Zone | FARO Technologies, Inc. |
| .D2D | Unknown Developer | Ficheiros CAD | 3D Fassade Plus CAD Data | 3D Fassade Plus | Unknown Developer |
| .DAB | Epigon Media Technologies | Ficheiros CAD | Digital Audio Broadcasting Audio Data | DMB Player | Epigon Media Technologies |
| .DB1 | Trimble Inc. | Ficheiros CAD | Tekla Structures Model File | Tekla Structures BIM software | Trimble Inc. |
| .DB_ | Unknown Developer | Ficheiros CAD | CAD File | Unknown Software | Unknown Developer |
| .DC | IMSI/Design, LLC | Ficheiros CAD | DesignCAD Design File | IMSI DesignCAD 3D Max | IMSI/Design, LLC |
| .DC1 | DevCad | Ficheiros CAD | DevCad Document | DevCad Cam Pro | DevCad |
| .DC2 | Kodak | Ficheiros CAD | Kodak Digital Camera RAW Image File | Adobe Photoshop | Adobe Systems Incorporated |
| .DC3 | IMSI/Design, LLC | Ficheiros CAD | DesignCAD 3D ASCII Drawing | IMSI DesignCAD 3D Max | IMSI/Design, LLC |
| .DC5 | BIGAL | Ficheiros CAD | DynaCAD CAD Document | DynaCAD | BIGAL |
| .DCD | IMSI/Design, LLC | Ficheiros CAD | DesignCAD Drawing | IMSI DesignCAD 3D Max | IMSI/Design, LLC |
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