LanguageTool

Freemium

languagetool.org

A highly robust, open-source AI grammar and style checker that provides unparalleled, privacy-focused correction across more than 30 languages.

About LanguageTool

LanguageTool is the definitive open-source alternative to massive corporate grammar checkers like Grammarly. While most grammar AI focuses exclusively on the English language, LanguageTool was engineered from the ground up by a massive global open-source community to be a linguistic powerhouse, offering flawless grammar and style correction in over 30 languages, including complex languages like German, Russian, and Arabic.

The platform's primary competitive advantage is absolute privacy. Because the core engine is open-source, highly secure enterprises (like defense contractors or law firms) can download the software and run the AI entirely on their own internal, offline servers. This guarantees that highly confidential text never leaves the building.

For standard users, it provides a highly polished browser extension and native Mac/Windows apps. It utilizes advanced AI to not only fix typos but to recognize context—for example, accurately distinguishing between the incorrect use of 'their' and 'there' based entirely on the surrounding sentence structure.

Key Features

Core capabilities and technical highlights of LanguageTool

Unparalleled multilingual support providing deep grammar, styling, and contextual spellchecking across more than 30 global languages.

Open-source core architecture allowing enterprise teams to self-host the entire AI engine locally for absolute data privacy and compliance.

Advanced AI paraphrasing and sentence rewriting capabilities available natively in multiple major languages (English, German, Spanish).

Ubiquitous integration ecosystem featuring robust plugins for browsers, Microsoft Word, Google Docs, LibreOffice, and massive developer APIs.

Popular Use Cases

How teams, developers, and creators get value from LanguageTool

1Install the browser extension to automatically check complex German grammar and formal (Sie) styling while drafting a corporate email.

2Deploy the open-source version locally on an enterprise server to provide grammar checking for a law firm without violating strict client data privacy laws.

3Utilize the advanced AI paraphrasing tool to instantly rewrite a clunky, poorly translated Spanish sentence into a fluent, native-sounding structure.

4Integrate the robust API into a custom Content Management System (CMS) to automatically spellcheck all user-submitted reviews in 15 different languages.

Frequently Asked Questions

Common questions and answers regarding LanguageTool

Is LanguageTool free?

Yes, the core web editor and browser extensions are free for basic grammar checking. The Premium tier unlocks the advanced AI paraphrasing and removes character limits.

Why use this instead of Grammarly?

The two main reasons are multilingual support (Grammarly only supports English) and absolute privacy (you can run LanguageTool offline on your own servers).

Is it difficult to self-host?

For a developer, it is relatively simple; the open-source Java-based server can be deployed locally using standard Docker containers.

Does it understand different English dialects?

Yes, you can explicitly set the tool to check against US, British, Australian, or Canadian English, ensuring local spelling variations (like 'color' vs 'colour') are respected.

Does it have an AI writing assistant?

Yes, they have heavily integrated AI to offer advanced sentence rewriting and paraphrasing, though it focuses more on correction than generating long-form content from scratch.