The Flow website is built using Jekyll.

Many of our docs are written as JS files, in which comments are converted to markdown and JS is typechecked by Flow and shown as syntax-highlighted code blocks with any Flow errors displayed inline. We use a custom plugin to build these .doc.js files.

So, Flow must be installed and on your path. See the instructions on GitHub.

Many systems ship with a fairly old version; we use 2.2 to build and deploy the site. One way to get a recent version is to use rvm:

gpg --keyserver hkp://keys.gnupg.net --recv-keys 409B6B1796C275462A1703113804BB82D39DC0E3
\curl -sSL https://get.rvm.io | bash -s stable --ruby=2.2

# from this directory (website/)
gem install bundler
bundle install

jekyll serve -w

This will fire up a web server at http://localhost:8000 by default. To access it from other machines, add --host :: (all interfaces, including IPv6).

The -w flag watches the filesystem for changes, so pages will rebuild on save. It takes a few seconds, but just refresh the page to see changes.

On each commit, Travis builds the site and then pushes the results to the gh-pages branch. Then GitHub Pages deploys the changes to http://flowtype.org.