MODFLOW 6  version 6.5.0.dev2
MODFLOW 6 Code Documentation
MODFLOW 6 Source Code Documentation

The documentation here is extracted from the source code by doxygen.

The source code repository is hosted at https://github.com/MODFLOW-USGS/modflow6 where full details can be found.

MODFLOW 6 usage documentation can be found at https://modflow6.readthedocs.io/en/latest/