This is an ASP.NET Core application, however, it references the full .NET Framework currently (instead of .NET Core which is full cross platform). I am working to make it run on .NET Core but it requires some third party library dependencies to be addressed first. This is being tracked here https://github.com/bitwarden/core/issues/3 . I anticipate this to run on .NET Core in the near future and therefore be truly cross platform for Windows, Mac, and Linux.