What is LanguageTool used for?

LanguageTool is open-source proofreading software that checks grammar and style in English, Spanish, French, German and more than 20 other languages. It is a good fit for proofreading text in editors and apps, and private grammar checking on your own server.

Is LanguageTool open source?

Yes. LanguageTool is open source under the LGPL-2.1 licence. Its source code is on GitHub at languagetool-org/languagetool and is written mainly in Java.

Is LanguageTool free?

Yes. LanguageTool is open source, so the software itself is free to use. A managed cloud version is also available.

Can I self-host LanguageTool?

Yes. LanguageTool can be self-hosted on your own server or infrastructure.

What is LanguageTool an alternative to?

LanguageTool is an open-source alternative to Grammarly, ProWritingAid, QuillBot and Wordtune. Other open-source alternatives to ProWritingAid include RedPen.

Is LanguageTool actively maintained?

Yes. The most recent commit to LanguageTool was on 2 October 2026. The project has 15k stars on GitHub.

LanguageTool: open-source alternative to Grammarly

About LanguageTool

LanguageTool is open-source proofreading software that finds grammar and style errors a simple spell checker would miss. It supports English, Spanish, French, German, Portuguese, Polish, Dutch and more than 20 other languages. The core is written in Java and freely available under the LGPL 2.1 or later.

It can be used in several ways. The project documents how to run your own LanguageTool server, an HTTP API for sending text to a server, a public server that can be used over HTTP, and a Java API with Javadoc. Error detection works through rules, and the development overview explains how to contribute new rules for a language.

Community-contributed Docker files are listed for people who want to run a containerized server. Building from source needs Java 17 and Apache Maven, and the README offers a scripted install as well as a shallow clone option to reduce download size, since a complete clone is large. A forum is available for questions.

Key features

Grammar and style checking
Support for 25+ languages
HTTP API for integrations
Run your own LanguageTool server
Java API with Javadoc
Community Docker images

Good fit for

→Proofreading text in editors and apps
→Private grammar checking on your own server

Built with: Java
Tags: grammar; proofreading; spellcheck; style-checker; nlp; java; languages; api

LanguageTool: questions and answers

What is LanguageTool used for?: LanguageTool is open-source proofreading software that checks grammar and style in English, Spanish, French, German and more than 20 other languages. It is a good fit for proofreading text in editors and apps, and private grammar checking on your own server.
Is LanguageTool open source?: Yes. LanguageTool is open source under the LGPL-2.1 licence. Its source code is on GitHub at languagetool-org/languagetool and is written mainly in Java.
Is LanguageTool free?: Yes. LanguageTool is open source, so the software itself is free to use. A managed cloud version is also available.
Can I self-host LanguageTool?: Yes. LanguageTool can be self-hosted on your own server or infrastructure.
What is LanguageTool an alternative to?: LanguageTool is an open-source alternative to Grammarly, ProWritingAid, QuillBot and Wordtune. Other open-source alternatives to ProWritingAid include RedPen.
Is LanguageTool actively maintained?: Yes. The most recent commit to LanguageTool was on 2 October 2026. The project has 15k stars on GitHub.