NOTICE This add-on does not work pending a bug and is therefore not available as an add-on for Firefox. Please, see the following alternatives:
END OF NOTICE
Based on the text entered in a textarea, this add-on automatically detects the language and sets the corresponding spell checking dictionary. You need to type at least 25 characters before the add-on will start. Before that limit is reached, it disables spell checking. A small icon on the extension's icon will give you feedback about the language that has been detected.
Get more details at https://addons.mozilla.org/en-US/firefox/addon/automatic-dictionary-switcher/
This add-on is implemented using cfx.
It uses the following files that are taken from other Open Source and Creative Commons sources:
lib/franc-most.js - language identification by Titus Wormer released under MIT license (https://github.com/wooorm/franc).lib/iso6393.js - languages codes, based on JSON by Titus Wormer released under MIT license (https://github.com/wooorm/iso-639-3).data/img/dictionary.png - based on icon by Farhat Datta, released under a Creative Commons like license: Relax-Attribution / Share Alike / Semi-Noncommercial, see http://www.languageicon.org for details.