Parts Library

LeoCAD is completely compatible with LDraw's parts library. In fact, the library included in the installer packages is just a ZIP archive of LDraw's library without any changes.

This is mostly done to simplify things so that new users do not need to download and install a separate file or worry about updating their library. Many LeoCAD users are young people without a lot of computer experience, so the setup process is kept as simple as possible.

At the same time, there are also experienced users who like to maintain their own libraries with unofficial parts that they create or download from the internet. Those people can still use their LDraw library with LeoCAD, all they need to do is tell LeoCAD where to find it.

Note that there is a performance advantage for using a zip file for the library, as the application will take less time to start, and the models will load faster.

Using a Custom Parts Library

There are several ways to specify a custom library folder or file (in order of priority):

  • Use the “-l” command line option, followed by the library path.
  • Set the “LEOCAD_LIB” environment variable.
  • Enter a new library path in the “Preferences” menu.

Note that LeoCAD can use either a zip file or a regular folder for its library. Here are some examples:

$ leocad -l C:\LDraw\
$ set LEOCAD_LIB=C:\User\Downloads\

Unofficial Parts

You can easily use unofficial LDraw parts with LeoCAD:

If you are using LeoCAD's default library, then you will need to download the current unofficial parts from and then place “” in the same folder where “ library.bin” is located and restart LeoCAD. The next time the application starts, it will detect “” and load it automatically.

If you are using your own custom library with loose files, then all you need to do is place the files in the “unofficial” folder. The parts should be visible the next time you start LeoCAD.

Default Library Path

The default library path is different for each operating system:

Windows: The application looks for “library.bin” in the same folder where “LeoCAD.exe” is located.

Linux: The path is “../share/leocad/library.bin”, which is relative to the application binary folder. If you have the LeoCAD executable “/usr/bin/leocad”, the application will look for the library in “/usr/share/leocad/library.bin”.

macOS: The application bundle should have a “library.bin” file in the “Contents/Resources” folder.