| .ATC | Autodesk, Inc. | Settings Files | AutoCAD Tool Catalog File | Autodesk AutoCAD Civil 3D | Autodesk, Inc. |
| .CLT | Clarity Legal | Page Layout Files | Clarity Legal Transcript File | Autodesk AutoCAD Civil 3D | Autodesk, Inc. |
| .COF | Microchip Technology Inc. | Executable Files | MPLAB COFF File | Autodesk AutoCAD Civil 3D | Autodesk, Inc. |
| .DAB | Epigon Media Technologies | Audio Files | Digital Audio Broadcasting Audio Data | Autodesk AutoCAD Civil 3D | Autodesk, Inc. |
| .DCN | Autodesk, Inc. | Settings Files | Autodesk Depth Slope Definition | Autodesk AutoCAD Civil 3D | Autodesk, Inc. |
| .DFM | Open Source | Text Files | Pascal File | Autodesk AutoCAD Civil 3D | Autodesk, Inc. |
| .FBK | Microsoft Corporation | Backup Files | Microsoft Dynamics NAV Backup File | Autodesk AutoCAD Civil 3D | Autodesk, Inc. |
| .HDC | TCD Labs | Data Files | HD Tach Benchmark Results | Autodesk AutoCAD Civil 3D | Autodesk, Inc. |
| .HTP | Autodesk, Inc. | CAD Files | Autodesk Slope Template Definition | Autodesk AutoCAD Civil 3D | Autodesk, Inc. |
| .ICN | Microsoft Corporation | Raster Image Files | Windows Icon File | Autodesk AutoCAD Civil 3D | Autodesk, Inc. |
| .INP | Concept Software | Page Layout Files | Urdu InPage Document | Autodesk AutoCAD Civil 3D | Autodesk, Inc. |
| .LK# | Autodesk, Inc. | CAD Files | Autodesk Multi-User Coordination Lock Data | Autodesk AutoCAD Civil 3D | Autodesk, Inc. |
| .PDA | Molecular Devices | Data Files | SoftMax Pro Microplate Data Analysis File | Autodesk AutoCAD Civil 3D | Autodesk, Inc. |
| .PFB | Adobe Systems Incorporated | Font Files | Printer Font Binary File | Autodesk AutoCAD Civil 3D | Autodesk, Inc. |
| .PSP | Corel Corporation | Raster Image Files | PaintShop Pro Image | Autodesk AutoCAD Civil 3D | Autodesk, Inc. |
| .RAT | World Wide Web Consortium (W3C) | Uncommon Files | PICS Rating File | Autodesk AutoCAD Civil 3D | Autodesk, Inc. |
| .RTC | Brain Innovation | Data Files | BrainVoyager QX Design Matrix File | Autodesk AutoCAD Civil 3D | Autodesk, Inc. |
| .SDC | Stardock Corporation | Backup Files | Stardock Central Download Archive | Autodesk AutoCAD Civil 3D | Autodesk, Inc. |
| .SDF | Microsoft Corporation | Database Files | SQL Server Compact Database File | Autodesk AutoCAD Civil 3D | Autodesk, Inc. |
| .SHX | Autodesk, Inc. | CAD Files | AutoCAD Compiled Shape File | Autodesk AutoCAD Civil 3D | Autodesk, Inc. |
| .SLP | Magix Software GmbH | Audio Files | SpectraLayers Pro Project | Autodesk AutoCAD Civil 3D | Autodesk, Inc. |
| .SSC | Microsoft Corporation | Developer Files | SourceSafe Status File | Autodesk AutoCAD Civil 3D | Autodesk, Inc. |
| .TBL | Blizzard Entertainment Inc. | Data Files | StarCraft Information Table | Autodesk AutoCAD Civil 3D | Autodesk, Inc. |
| .TDF | DVD Copy | Settings Files | Title Definition Format File | Autodesk AutoCAD Civil 3D | Autodesk, Inc. |
| .XSP | Open Source | Audio Files | Kodi Smart Playlist File | Autodesk AutoCAD Civil 3D | Autodesk, Inc. |
| .XTP | adnx | Data Files | xTime Project Document | Autodesk AutoCAD Civil 3D | Autodesk, Inc. |
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