Why do I get a "Multiple precompiled assemblies" error in Unity?

When importing Tridify BIM Tools into a Unity project, some versions of Unity 2020 and 2021 give an error: PrecompiledAssemblyException: Multiple precompiled assemblies with the same name Newtonsoft.Json.dll included or the current platform. Only one assembly with the same name is allowed per platform.

Here's how to get the plugin to work normally:

  • Open a new project or delete the Tridify folder from your project's Assets folder
  • In Unity's Package Manager, select Tridify BIM Tools and click Import
  • In the Import Unity Package window, go to Tridify>Plugins and deselect Newtonsoft.Json.dll
  • Import the package