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 check the contents of buffers, and reports warnings and errors directly in the buffer, or in an optional error list. The following screenshot shows Flycheck at work in an Emacs Lisp buffer, with with the Solarized Light color theme and the Source Code Pro font:

• Supports over 30 programming and markup languages with more than 60 different syntax checking tools
• Fully automatic, fail-safe, on-the-fly syntax checking in background
• Nice error indication and highlighting
• Optional error list popup
• Many customization options
• A comprehensive manual
• A simple interface to define new syntax checkers (extending)
• A “doesn't get in your way” guarantee
• Many 3rd party extensions

Install Flycheck from MELPA or Marmalade with:

M-x package-install RET flycheck

In your Cask file:

(source gnu)
(source melpa)

(depends-on "flycheck")

You need GNU Emacs 24 on a Unix system (Linux, OS X, …), and additional external programs for the languages you use. See Installation and Supported languages for more information.

Flycheck does not support GNU Emacs 23, other flavors of Emacs, or Windows.

Documentation is available at http://flycheck.readthedocs.org:

• Quick start (tutorial)
• User manual (reference information)

• Issue tracker
• Github
• Contribution guidelines

• Contributors
• Credits

This program 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.

This program 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.

The Flycheck documenation is free documentation: you can copy, distribute and/or modify it under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is available at https://github.com/flycheck/flycheck/blob/master/doc/fdl.txt.

Alternatively, 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.