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 (see Flycheck manual for more information):

Out of the box Flycheck supports over 40 different programming languages with more than 80 different syntax checking tools, and comes with a simple interface to define new syntax checkers.

Many 3rd party extensions provide new syntax checkers and other features like alternative error displays or mode line indicators.

Try out

Flycheck needs GNU Emacs 24.3 or newer, and works best on Unix systems. Windows users, please be aware that Flycheck does not support Windows officially, although it should mostly work fine on Windows. See Windows support and watch out for known Windows issues!

Install some syntax checker tools and type the following in your *scratch* buffer and run M-x eval-buffer:

(require 'package)
(add-to-list 'package-archives
             '("melpa" . "http://stable.melpa.org/packages/") t)
(package-initialize)
(package-refresh-contents)

(package-install 'flycheck)

(global-flycheck-mode)

For a more gentle introduction read the Installation instructions and go through Quickstart guide.

Support & Contribution

Please ask questions about Flycheck on Stack Exchange or in our Gitter chat. We try to answer all questions as fast and as precise as possible.

To report problems or bugs, please use our issue tracker. Our Contributor’s Guide helps you to create good bug reports; please take a look.

We welcome patches and pull requests that fix bugs or provide new features. Please read our Contributor’s Guide for help and guidance before submitting pull requests. When making larger changes to Flycheck or implementing new features we recommend that you first open a separate issue or ask in our Gitter channel to discuss you intended changes.

All contributors and all participants in our communication channels are expected to follow our Code of Conduct.

License

Flycheck is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

Flycheck is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.

See COPYING for details.

You may copy, distribute and/or modify the Flycheck documentation under the terms of the Creative Commons Attribution-ShareAlike 4.0 International Public License. A copy of the license can be obtained at https://creativecommons.org/licenses/by-sa/4.0/legalcode.

Permission is granted to copy, distribute and/or modify the Flycheck logo in /flycheck.svg under the terms of the Creative Commons Attribution-ShareAlike 4.0 International Public License. A copy of the license can be obtained at https://creativecommons.org/licenses/by-sa/4.0/legalcode.