Third Party Libraries

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These are libraries which are not changed in the FreeCAD project. They are basically used unchanged as a dynamic link library (*.so or *.dll). If there is a change necessary or a wrapper class is needed, then the code of the wrapper or the changed library code has to be moved to the FreeCAD base package. The used libraries are:

If you are using Windows, consider using LibPack instead of downloading and installing all the stuff on your own.


Link table
Lib name Version needed Link to get it
Python >= 2.5.x
OpenCasCade >= 5.2
Qt >= 4.1.x
Coin3D >= 2.x
SoQt >= 1.2
Xerces-C++ >= 2.7.x < 3.0
Zlib >= 1.x.x
Boost >= 1.33.x
Eigen3 >= 3.0.1
Shiboken >= 1.1.2
libarea N/A



Version: 2.5 or higher

License: Python 2.5 license

You can use the source or binary from or use alternetivly ActiveState Python from though it is a little bit hard to get the debug libs from ActiveState.


Python is the primary scripting language and is used throughout the application. For example:

  • Implement test scripts for testing on:
    • memory leaks
    • ensure presents of functionality after changes
    • post build checks
    • test coverage tests
  • Macros and macro recording
  • Implement application logic for standard packages
  • Implementation of whole workbenches
  • Dynamic loading of packages
  • Implementing rules for design (Knowledge engineering)
  • Doing some fancy Internet stuff like work groups and PDM
  • And so on ...

Especially the dynamic package loading of Python is used to load at run time additional functionality and workbenches needed for the actual tasks. For a closer look to Python see: Why Python you may ask. There are some reasons: So far I used different scripting languages in my professional life:

  • Perl
  • Tcl/Tk
  • VB
  • Java

Python is more OO then Perl and Tcl, the code is not a mess like in Perl and VB. Java isn't a script language in the first place and hard (or impossible) to embed. Python is well documented and easy to embed and extend. It is also well tested and has a strong back hold in the open source community.


Goes to Guido van Rossum and a lot of people made Python such a success!


Version: 5.2 or higher

License: v6.7.0 and later are governed by GNU Lesser General Public License (LGPL) version 2.1 with additional exception. Earlier versions use a slightly different license:

OCC is a full-featured CAD Kernel. Originally, it's developed by Matra Datavision in France for the Strim (Styler) and Euclid Quantum applications and later on made Open Source. It's a really huge library and makes a free CAD application possible in the first place, by providing some packages which would be hard or impossible to implement in an Open Source project:

  • A complete STEP compliant geometry kernel
  • A topological data model and all needed functions to work on (cut, fuse, extrude, and so on. . . )
  • Standard Import- / Export processors like STEP, IGES, VRML
  • 3D and 2D viewer with selection support
  • A document and project data structure with support for save and restore, external linking of documents, recalculation of design history (parametric modeling) and a facility to load new data types as an extension package dynamically

To learn more about OpenCasCade take a look at the OpenCasCade page or


Version: 4.1.x or higher

License: GPL v2.0/v3.0 or Commercial (from version 4.5 on also LPGL v2.1)

I don't think I need to tell a lot about Qt. It's one of the most often used GUI toolkits in Open Source projects. For me the most important point to use Qt is the Qt Designer and the possibility to load whole dialog boxes as a (XML) resource and incorporate specialized widgets. In a CAX application the user interaction and dialog boxes are by far the biggest part of the code and a good dialog designer is very important to easily extend FreeCAD with new functionality. Further information and a very good online documentation you'll find on

Shiboken and Pyside

Shiboken (Shi bō ken, 死某剣) is the Python binding generator that Qt for Python uses to create the PySide module, in other words, is the system we use to expose the Qt C++ API to Python.

The name Shiboken2 and PySide2 make reference to the Qt 5 compatibility, since the previous versions (without the 2) refer to Qt 4. Read more about Shiboken and Pyside on Qt for Python wiki page


Version: 2.0 or higher

License: GPL v2.0 or Commercial

Coin is a high-level 3D graphics library with a C++ Application Programming Interface. Coin uses scenegraph data structures to render real-time graphics suitable for mostly all kinds of scientific and engineering visualization applications.

Coin is portable over a wide range of platforms: any UNIX / Linux / *BSD platform, all Microsoft Windows operating system, and Mac OS X.

Coin is built on the industry-standard OpenGL immediate mode rendering library, and adds abstractions for higher-level primitives, provides 3D interactivity, immensely increases programmer convenience and productivity, and contains many complex optimization features for fast rendering that are transparent for the application programmer.

Coin is based on the SGI Open Inventor API. Open Inventor, for those who are not familiar with it, has long since become the de facto standard graphics library for 3D visualization and visual simulation software in the scientific and engineering community. It has proved it's worth over a period of more than 10 years, its maturity contributing to its success as a major building block in thousands of large-scale engineering applications around the world.

We will use OpenInventor as 3D viewer in FreeCAD because the OpenCasCade viewer (AIS and Graphics3D) has serios limitations and performace bottlenecks, especially when it goes in large-scale engineering rendering. Other things like textures or volumetric rendering are not really supported, and so on ....

Since 2011, Coin has been licenced under the OSI approved 3-clause BSD licence.


Version: 1.2.0 or higher

License: GPL v2.0 or Commercial

SoQt is the Inventor binding to the Qt Gui Toolkit. Unfortunately, it's not longer LGPL so we have to remove it from the code base of FreeCAD and link it as a library. It has the same licence model like Coin. And you have to compile it with your version of Qt.


Version: 2.7.0 or higher

License: Apache Software License Version 2.0

Xerces-C++ is a validating XML parser written in a portable subset of C++. Xerces-C++ makes it easy to give your application the ability to read and write XML data. A shared library is provided for parsing, generating, manipulating, and validating XML documents.

Xerces-C++ is faithful to the XML 1.0 recommendation and many associated standards (see Features below).

The parser provides high performance, modularity, and scalability. Source code, samples and API documentation are provided with the parser. For portability, care has been taken to make minimal use of templates, no RTTI, and minimal use of #ifdefs.

The parser is used for saving and restoring parameters in FreeCAD.


Version: 1.x.x

License: zlib License

zlib is designed to be a free, general-purpose, legally unencumbered -- that is, not covered by any patents -- lossless data-compression library for use on virtually any computer hardware and operating system. The zlib data format is itself portable across platforms. Unlike the LZW compression method used in Unix compress(1) and in the GIF image format, the compression method currently used in zlib essentially never expands the data. (LZW can double or triple the file size in extreme cases.) zlib's memory footprint is also independent of the input data and can be reduced, if necessary, at some cost in compression.


Version: 1.33.x

License: Boost Software License - Version 1.0

The Boost C++ libraries are a collection of peer-reviewed, open source libraries that extend the functionality of C++. The libraries are licensed under the Boost Software License, designed to allow Boost to be used with both open and closed source projects. Many of Boost's founders are on the C++ standard committee and several Boost libraries have been accepted for incorporation into the Technical Report 1 of C++0x.

The libraries are aimed at a wide range of C++ users and application domains. They range from general-purpose libraries like SmartPtr, to OS Abstractions like FileSystem, to libraries primarily aimed at other library developers and advanced C++ users, like MPL.

In order to ensure efficiency and flexibility, Boost makes extensive use of templates. Boost has been a source of extensive work and research into generic programming and meta-programming in C++.

See: for details.


Version: N/A

License: New BSD (BSD 3-Clause)

Area is a piece of software created by Dan Heeks for HeeksCNC. It is employed as a library for generation of CAM related operations in the Path Workbench.


LibPack is a convenient package with all the above libraries packed together. It is only needed if you are building on the Windows Platform and you can find it at If you're working under Linux you have to use the package repositories of your Linux distribution, i.e. no libPack needed and offered for Linux.

FreeCADLibs7.x Changelog

  • Using QT 4.5.x and Coin 3.1.x
  • Eigen template lib for Robot added
  • SMESH experimental