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CAD File Formats

CAD File Formats

CAD file formats are important because not all formats are interchangeable. Some formats can only be viewed in specific CAD applications. (To learn about how to convert from one CAD format to another, click here.)

Have you ever worked with CAD? If yes, you’re already likely to be familiar with some of AutoCAD’s most common file format, such as DWG and DXF. These aren’t the only file extensions and formats used with AutoCAD, though. In fact, there are some formats that many people are not entirely familiar with. What is a file format actually? Is a file format different than a file extension? If you are lost with such kinds of questions, this article is for you.

File Extension:

A file extension is a group of characters after a file name, e.g. if there is a file in Windows named ‘article,’ and you find it as ‘article.docx,’ then ‘.docx’, is the file extension. This file extension, ‘.docs’ lets Windows know that which program on your computer the file, ‘article’ can be open with. Here, extension ‘.docx’ should be open with Microsoft Word.

File Format:

Every file in a computer is created as a particular type ort format. Typically file extensions are used to determine the file format or file type. For example, if you have an extension, ‘.docx’ or ‘.doc,’ you must be dealing with Microdoft Word. Most often, an extension is associated with only one type or a more popular file format. Such as, ‘.pdf’ extension deals either with, ‘portable Document Format,’ or a ‘a printer description type.’ This is the reason the two terms, file extension and file format, are often used interchangeably.

What Is A CAD File?

CAD is an image file format used by AutoCAD, which is generated by CAD software programs and also creates 2D and 3D designs for models or architecture plans. CAD files hold information for these images; 2D CAD files are often referred to as drawings, whereas 3D files are called models, parts, or assemblies. CAD stands for Computer Aided Design.

Why is CAD File Format Important?

While creating any kind of document using a computer, you must save the same as a file. This file contains all the necessary information related to the document as well as the way it should be processed and visualized.

CAD file formats are also extremely important when considering CAD design. When using programs such as AutoCAD or SolidWorks, you are creating a digital document. This document is then saved as a specific type of file format.

CAD file format apprises which program you can use to view the document. Moreover, it informs about the content of the document. For a CAD file, that means the design itself.

Each CAD system has its own method of describing geometry, both mathematically and structurally. CAD files hold information for these processes, as well as drafting information.

As mentioned above, there are 2 dimensional (2D) and 3 dimensional (3D) file formats. As the name suggests, in a 2 dimensional system you are operating under 2 axes only. The resulting file is a layout/draft of the object being designed.

In a 3 dimensional (3D) environment the object is more visual as we have added another axis into the system. The objects seem real and curvatures, texture and all complex surface features are easily visible.

Usually components are designed in a 3D environment and production is conveyed in 2D format called production drawings. Latest production techniques can work from the 3D data itself which is called CAM (Computer Aided Manufacturing).

Categories of CAD File Formats:

CAD file formatting states, how the design will be viewed within a particular program such as AutoCAD or SolidWorks. There are two main categories of CAD file formats:
– Proprietary
– Non-proprietary (or neutral).

Proprietary Vs. Non-proprietary

Have you ever heard the terms, ‘proprietary goods’ and ‘non-proprietary goods?’

Proprietary goods are made and sent out by a particular company whose name is on the product. On the contrary, at its most basic definition, non-proprietary is defined as a generic good type.

What do these two terms mean in the context of CAD file formats?

There are some CAD programs, which use proprietary file formats. These are the file formats that have been created solely for use on that one program. This file is generated and coded in such a way that it can only be opened using that particular program, which is used while creating it. If you try to open a proprietary file in another program, you receive an error.

Proprietary CAD file format contains everything from the original design; nothing will be left out. This type of file is useful for sharing designs within the company and every user must have access to the same program. Hence, in this case a neutral file format is not needed.

A neutral or non-proprietary file format is not exclusive to one CAD program. It is considered as vendor neutral and can be opened in different programs that can read it. This type of CAD file format generally uses generic information and standardized protocols so that many programs will understand the contents within.

Non-proprietary or neutral CAD file formats are useful when you need to share the documents with external sources. You may, for example, wish to share a CAD product design with a customer, who has not the access to that particular CAD program. If the design is shared as a non-proprietary format, they are still able to open the file.

Most Popular Proprietary CAD File Formats:

1) SolidWorks

The SolidWorks file format is a proprietary file for the SolidWorks CAD software that runs on Windows systems. This CAD program was first released in 1995. It is one of the longest-running CAD program and still widely used throughout many industries. SolidWorks is capable of creating both 2D and 3D drawings. The proprietary SolidWorks file format is regularly used, but they have also released a popular neutral format as well.

2) Autodesk Inventor

This is another hugely popular designing program and is used to create 3D documentation and realistic scale models of parts as well as components. Moreover, this program is compatible with BIM, which is currently an exploding file format in the construction industry.

3) Solid Edge

The proprietary file format for this program is Solid Edge. The file extensions for this formats are ASM, PAR, PASM, and PWD.

Some Popular Neutral File Formats:


STEP is one of the most widely used CAD file format. This format is created in conjunction with ISO 10303. ISO 10303 is the standard for computer representations of product manufacturing information. Most modern CAD software supports this file format. STEP can support both single file and assembly formats. It also can contain a Bill of Materials (BOM).

2) VRML (Virtual Reality Modeling Language)

This tupe of non-proprietary file format is actually used for the representation of 3D graphics and interactive vector graphics, which is developed in conjunction with the Web3D Consortium. The VRML file format is usually used for web graphics, which can specify surface color, textures, transparency, and other important graphical concepts.

VRML and its successor X3D have become international standards (ISO). This format is first specified in 1994. X3D is approved later on in 2005. Both file formats are non-proprietary and can be opened with a variety of programs.


IGES (pronounced as eye-jess) is another popular non-proprietary format. This format is first developed in 1980 and widely used in the CAD industry since then. It is developed exclusively by the US Airforce, but once they have started to use other technology, the format is taken over by ANSI.

This file format is used to display wireframes and circuit diagrams. Because of its lack of color rendering and textures, it should generally not be used to share designs with third-party organizations, unless they know the design process or the product.

AutoCAD’s Common File Types: DWG and DXF


DWG is used as an abbreviation for ‘Drawing,’ which is a proprietary vector file format created by Autodesk in 1982. Developers need a license to access this format in their software. DWG files are smaller than DXF files due to their binary makeup. Users can view and edit DWG files with other programs too, including Scan2CAD, though they are designed to be used in AutoCAD.


Drawing Exchange Format, DXF, is a vector file format and was created by Autodesk as an exchange medium between different types of CAD software. It is an open standard, so it’s supported by practically every CAD programs in the market. You can also view DXF files using a range of programs including Adobe Illustrator and Scan2CAD. While DXFs are smaller than their raster counterparts, they’re typically larger than DWGs. Why? Because DXFs are made up of ASCII text, whereas DWGs are binary.

Some More File Formats for Sharing 2D and 3D CAD Designs:


Stereo Lithography, is a universal format. It is a format for pure 3D information that has been specifically created by 3D programs. STL is concerned with surface geometry and shapes. It cannot be used to represent color or textures. This file format is fine for use in basic situations where complicated CAD data is not required.


X3D actually replaces the non-proprietary file format of VRML. Although, VRML was popular, yet limited to only a number of different software packages. X3D is also a neutral file format and is used to represent 3D computer graphics in an XML format. It can be used to encode graphical scenes with the XML syntax, and it allows integration with a number of different APIs as well.


The Portable Document Format is proprietary to Adobe but has a wide array of uses. PDF files can be converted into AutoCAD files. CAD files can also be exported into PDFs for easy viewing. If you want to simply showcase a 2D design to a customer or someone without CAD knowledge, a PDF file is suitable. Many CAD programs allow you to export your work to a PDF.

Some File Extensions That Are Developed For and Associated With AutoCAD

1. CAD Standards File:
• DIM — Exported Dimension Style file (DIMEX/DIMIM commands).
• LAS — Exported Layer State file (LAYERSTATE command).
• LIN — Linetype file (LINETYPE command).
• MLN — Multiline Style file (MLINE command).
• NFL — Custom Filters file (FILTER command).
• PAT — Hatch Pattern file (HATCH command).

2. Customization Files:

a) Tool Palette-Related
• ATC — Tool Palette Catalog file.
• XTP — Exported Tool Palette file (CUSTOMIZE command).
• CUIx — Customization file (CUI command).
• DBX — ObjectDBX file.

b) Library-Related
• CBL — Content Browser Library file.
• DLL — Menu Resource Library or .NET Assembly.
• SLB — Slide Library file.
• SLD — Slide file (MSLIDE command).

c) Auto LISP-Related
• FAS — Fast-load AutoLISP file.
• LSP — AutoLISP Source file.
• MNL — Menu LISP files.
• VLX — Compile AutoLISP project file (VLIDE command).
• DCL — Dialog Control Language file.
• DCE — Dialog Error Log file.

d) Shape-Related
• SHP — Source Shape file (SHAPE command).
• SHX — Compiled Shape file (COMPILE command).

e) Various
• ACTM — Action Macro file (ACTRECORD command).
• ARX — ObjectARX file.
• BMP — Bitmap file (BMPOUT command).
• DVB — VBA Project file (VBAIDE command).
• PGP — Program Parameters.
• SCR — Script file (SCRIPT command).

3. Drawing Files:
• DST — Drawing Sheet Set file (SHEETSET command).
• DS$ — Autosave.
• DWF — Drawing Web file.
• DWS — Drawing Standards file.
• CHX — Batch Standards Checker file.
• DWT — Drawing Template file.
• DXB — Drawing Interchange Binary file.

4. Plotting Files:
• DSD — Publish Set file (PUBLISH command).
• PC3 — Plot Configuration files.
• PLT — Plot file.
• PSS — Plot Stamp Settings file (PLOTSTAMP command).
• PTW — Publish to Web Template file (PUBLISHTOWEB command).
• CTB — Color-dependent Plot Style file (PLOTSTYLE command).

5. Rendering Files:
• ADSKLIB — Materials Library file (MATBROWSEROPEN command).
• IES — Illuminating Engineering Society file (WEBLIGHT command).

Above is a list of a few file extensions that you may run into. Though it’s truly said that, “there are more CAD file formats than there are CAD design programs!”

Which Type of File Format should be used?

Now, the obvious question comes in the mind is, which type of file format should be used? The file format you should choose largely depends on the type of CAD program you’re using. You may have to use a proprietary file format. For example, you may want to work exclusively with SolidWorks, which is a proprietary format. Or you could use non-proprietary formats such as STEP.

CAD File Format Conversion

We have experts who can convert CAD files from any format to any other format, and we offer a free trial of our service. If you’re looking for help in converting a CAD file, send it to us and we’ll be happy to assist you. For a free trial conversion (limit of one per customer), mention the following discount code: CAD-File-Format-Free.

Also, if you need help in converting from an image file (e.g PDF, PNG, TIF) to CAD (e.g. DWG), click here. This will take you to a page where we offer a free trial of our PDF to DWG conversion service. You will find a special discount code on that page.

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