CAD File

What are CAD files and how to open them

Are you having problems opening a CAD file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your CAD files.

What is a CAD file?

CAD files have multiple uses, and Autodesk QuickCAD Drawing is one of them. Read more about the other uses further down the page.

Autodesk QuickCAD Drawing

The .cad file extension is used for a 3D graphics file format associated with Computer-Aided Design (CAD) projects. These CAD files are also known as CAD drawings. They may be generated using CAD tools like the QuickCAD software from Autodesk, Inc. These .cad files contain digital 2D and 3D graphics as well as other pieces of data like details of materials, dimensions, and processes, among others that were used to create the CAD project.

Some CAD software tools continue to use the CAD file format for drawing-related files. However, as of this writing, more CAD programs use the DFX file format and the DWG file format for digital sketches and drawings that are used in CAD projects instead of these CAD files.

There may be CAD tools other than QuickCAD that can be used to create, open, edit and export these .cad files to more widely used CAD drawing file formats.

How to open CAD files

We have identified one CAD opener that is compatible with this specific type of CAD file.

Programs that open Autodesk QuickCAD Drawing files

Last updated: August 25, 2026

All known file formats using extension .CAD

While Autodesk QuickCAD Drawing is a popular type of CAD-file, we know of 10 different uses of the .CAD file extension. Different software may use files with the same extension for different types of data.

CADe_SIMU Project

The CADe_SIMU Project format is the native project file used by the CADe SIMU electrotechnical simulation program. It saves the complete electrical or control-logic diagram drawn by the user, including its components, wiring, symbol placements, and any simulation-state data. CADe SIMU is mainly employed by students and technicians to design and test circuits such as control schematics, automation layouts, and related components through simulation before any real-world implementation.

Files are created and read exclusively by CADe SIMU. The usual workflow inside the program is to draw or assemble a diagram using schematic symbols from built-in libraries, connect those components with wires, select power supplies (AC or DC), timers, relays and other electromechanical elements, then run a simulation to observe behavior, error checks, and current paths. The project file keeps all of these elements and layout information so that work can be saved, resumed, shared, or printed.

Technical identifier: Project files begin with the ASCII signature "CADe_SIMU*" at byte offset zero. This signature uniquely distinguishes them from other formats that also use the same file extension.

While we have not verified the apps ourselves yet, our users have suggested ten different CAD openers which you will find listed below.

CadStd Drawing

CadStd Drawing files are created by CadStd, a simple 2-dimensional drafting program made by Apperson & Daughters. These files store drawings made using tools like lines, arcs, circles, dimensions, and text, following ANSI drafting standards. Both CadStd Lite (the free version) and CadStd Pro (paid version) can write these files. CadStd Pro adds more advanced editing commands (trim, fillet, chamfer, offset, isometric projections) and allows larger drawings.

A .CAD (CadStd Drawing) file holds only vector (not raster) data: geometric shapes, measurements, and metadata like scale. Users typically work in CadStd to produce or modify the drawing, then may export it from CadStd to more widely used exchange formats (like DXF, HPGL, SVG or PDF) to share with other CAD tools or for printing.

The file format begins with the ASCII header "CADSTD" followed by the characters "TD" and a control byte (hex 1A) at the very start of the file.

CAD opener for Windows

We have identified one CAD opener that is compatible with this specific type of CAD file.

Diagsoft Space Shuttle Plot Data

We know that one CAD format is Diagsoft Space Shuttle Plot Data. We have not yet analyzed in detail what these files contain and what they are used for. We're working on it.

Drafix Windows CAD Drawing

Drafix Windows CAD Drawing files store vector-based 2D technical drawings created by Drafix Windows CAD (later also called Drafix CAD), a Windows-era CAD program by Foresight Resources / Softdesk. These drawings include geometric entities such as lines, arcs, circles, polylines, text elements, dimensions, and fill/hatch patterns; they often rely on layers, symbols, and internal object attribute databases. The purpose of these files is to preserve full drawing information so it can be edited later in Drafix or imported into newer CAD software via export functions.

These files are generated and saved by the Drafix Windows CAD program itself. Users typically open them in the same software for further editing. They can also be converted or exported into more modern or more widely used CAD formats such as DXF or DWG using the export capabilities built into Drafix or using file-conversion utilities.

The internal file structure begins with binary signatures identifying the version and type - for example the first byte is 0x0A at offset 0 and bytes 0x0000000B03 at offset 2. There is a header text block containing the string "Drafix Windows CAD," along with field identifiers like DOUBLE and SHORT that reflect numeric formats.

ExtraCAD Drawing

ExtraCAD Drawing files with the extension .CAD are proprietary design files produced by Finson's ExtraCAD software. They store two-dimensional and three-dimensional technical drawings, including geometric shapes, layers, dimensions, symbols, text, and supporting 3D solids. These drawings are saved in the native file format of ExtraCAD when creating new engineering or architectural designs.

Created exclusively by ExtraCAD, these files are meant to be edited further in ExtraCAD rather than in other programs. They're typically used throughout the drafting process to build up complex designs using the application's tools for primitives like lines, circles, ellipses, polylines, surface fills, and for 3D modeling features such as spheres, cones, cylinders, and Boolean operations. Once completed, designs can usually be exported into more widely used CAD formats like DWG or DXF.

Internally, an ExtraCAD Drawing file begins with a specific byte signature: at offset 0 it contains the ASCII string "ExtraCAD…DRAWING" preceded by some fixed bytes. This unique header helps distinguish it from other .CAD formats.

Programs that open these CAD files

We have identified one CAD opener that is compatible with this specific type of CAD file.

GenCAD Drawing

GenCAD Drawing is a plain-text PCB design interchange format created by Teradyne (formerly GenRad) for sharing printed circuit board layout data, particularly among tools used to generate test programs (such as in-circuit testing), inspection, and fabrication workflows. It encapsulates information about board shape, layer stacking, component placement, netlists, and other physical and electrical details into a single human-readable text file. Support tools like Teradyne's D2B suite and various CAM/CAD systems use GenCAD Drawing files to feed manufacturing and testing systems.

GenCAD Drawing files are generated by exporting capabilities in ECAD layout applications or via utilities that convert native layout designs into the GenCAD structure. Once produced, these files are used in downstream processes such as automatic test fixture programming, component inspection (AOI), bed-of-nails fixture creation, or device assembly, since they provide geometry, component, and connectivity information all in one file.

Internally, GenCAD Drawing files are made up of structured sections marked by identifiers like $HEADER, $BOARD, $PADS, $COMPONENTS, $SIGNALS, etc. The $HEADER section defines key metadata such as version (e.g. "GENCAD 1.4"), unit system, origin point, and file revision. Subsequent sections describe physical geometry (board outline, copper shape, artwork), component shapes and placement, pin layouts, net names, and routing where present. Coordinate values are expressed according to the units set in the header, which may be USER-defined, inches, thou, or millimeters.

A signature pattern that identifies GenCAD Drawing data includes ASCII text such as "$HEADER" at the file start (bytes 0 - 7 show "$HEADER"), along with keywords including "GENCAD", "DRAWING", "UNITS", "ORIGIN", "LAYERS", "BOARD", "LINE", "USER", "INTERTRACK", "TRANSLATOR" and "$ENDHEADER" appearing in the file.

IntroCAD Drawing

IntroCAD is a Computer-Aided Design software for the Commodore Amiga home computer.

KiCad Drawing

We know that one CAD format is KiCad Drawing. We have not yet analyzed in detail what these files contain and what they are used for. We're working on it.

Programs that open these CAD files

We have identified one CAD opener that is compatible with this specific type of CAD file.

Rad CAD Drawing

Rad CAD is a Computer-Aided Design software for MS-DOS by Matthew Ratcliff.

Various apps that use files with this extension

These apps are known to open certain types of CAD files. Remember, different programs may use CAD files for different purposes, so you may need to try out a few of them to be able to open your specific file.

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