1. This documentation
OpenFAST documentation is hosted on readthedocs, and is automatically generated from both the main and dev branches whenever new commits are added. Clicking on the bar on the lower left corner of the page reveals a panel (see image below) containing options to select the branch of the repository, download the documentation other formats (PDF, HTML, EPub), and link to other relevant websites.

While OpenFAST developer documentation is being enhanced here, developers are
encouraged to consult the legacy FAST v8
NWTC Programmer's Handbook
.
Instructions on obtaining and installing OpenFAST are available in
Installing OpenFAST, and documentation for verifying an installation with the
automated tests is at Testing OpenFAST.
The majority of this documentation is divided into two parts:
Directed towards end-users, this part provides detailed documentation regarding usage of the OpenFAST and its underlying modules, as well as theory and verification documentation.
The developer guide is targeted towards users wishing to extend the functionality provided within OpenFAST. Here you will find details regarding the code structure, API supported by various classes, and links to source code documentation extracted using Doxygen.