These instructions are appropriate for macOS users who already have anaconda (or miniconda) installed.

Instructions

Open a terminal configured for anaconda/miniconda, and type:

conda install -c mrtrix3 mrtrix3

Upgrading MRtrix3

Once installed, you can keep MRtrix3 up to date using the regular Anaconda tools:

conda update -c mrtrix3 mrtrix3

Note that it is necessary to specify the mrtrix3 channel with the -c mrtrix3 option when updating, otherwise the command will return indicating that the package is up to date, without giving any indication that it hasn’t actually checked the mrtrix3 channel.