LanguageTool is an open-source spell checker. It values user privacy, which makes it a worthy alternative to Grammarly and others. The extension is available for free, but you can additionally purchase a premium license with advanced checking functions.
The free version is quite enough for basic spell checking and typical grammar errors. Personally, as I write this article, the LanguageTool extension is active. Not only is it privacy-oriented and serves as an open-source alternative to other services, but it works very fast without affecting your performance.
The server side is open-source, but unfortunately the extension itself is not. The developers explained that they took this step because they didn’t want competitors to use their extension and not give anything in return.
LanguageTool is designed with an emphasis on simplicity. At the touch of a button or a keyboard shortcut, LanguageTool will check the spelling and grammar of the selected text. LanguageTool is compatible with almost any text, regardless of the source, including social networks such as Twitter or LinkedIn and online services such as Gmail.
List of supported languages: Ukrainian, English (Australian, Canadian, British, New Zealand, South African, American), French, German (Austrian, German, Swiss), Asturian, Belarusian, Breton, Galician, Greek, Danish, Spanish, Italian, Catalan (also Valencian), Chinese, Khmer, Dutch, Persian, Polish, Portuguese (Brazilian, Portuguese, Angolan, Mozambican), Romanian, Slovak, Slovenian, Tagalog, Tamil, Swedish, Tagalog, Swedish, Esperanto, and Japanese.
