Flycheck is a modern on-the-fly syntax checking extension for GNU Emacs 24, intended as replacement for the older Flymake extension which is part of GNU Emacs.

It uses various syntax checking and linting tools to automatically check the contents of buffers while you type, and reports warnings and errors directly in the buffer, or in an optional error list.

3rd party extensions

The following extensions provide additional cool features for Flycheck: