This is our old add-on. We recommend using the new one instead (completely rewritten and under a new license):

• Firefox: https://addons.mozilla.org/firefox/addon/languagetool/
• Chrome: https://chrome.google.com/webstore/detail/languagetool/oldceeleldhonbafppcapldpdifcinji
• Opera: https://addons.opera.com/extensions/details/grammar-and-spell-checker-languagetool/
• Edge: https://microsoftedge.microsoft.com/addons/detail/grammar-and-spell-checker/hfjadhjooeceemgojogkhlppanjkbobc