This package adds support for flow to flycheck. It requires flow>=0.20.0. To use it, add to your init.el: (require 'flycheck-flow) (add-hook 'javascript-mode-hook 'flycheck-mode) You want to use flow in conjunction with other JS checkers. E.g. to use with gjslint, add this to your init.el (flycheck-add-next-checker 'javascript-gjslint 'javascript-flow) For coverage warnings add this to your init.el (flycheck-add-next-checker 'javascript-flow 'javascript-flow-coverage)