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languagetool-org

languagetool-org/languagetool

Open-source grammar, spelling and style checker for English, Spanish, French, German and 20+ other languages, usable as a server, Java library or CLI.

Open-source alternative to:Grammarly

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What is it?

LanguageTool is open-source proofreading software that checks text for grammar, style and spelling errors in English, Spanish, French, German, Portuguese, Polish, Dutch and more than 20 other languages. It is designed to catch many mistakes that a simple spell checker cannot detect.

The project can be run in several ways. It ships as a standalone desktop application with a GUI and command-line mode, and it can be run as a self-hosted HTTP server with a documented API. A public server is also available over HTTP, and the core can be used from Java through its API. Community-maintained Docker images are linked from the repository.

The core repository is licensed under LGPL 2.1 or later. The repository also includes install and build scripts, Maven build instructions, and a Wikipedia package for checking articles.

Key features

  • 01Checks grammar, style and spelling in 25+ languages.
  • 02Can run as a self-hosted HTTP server with a documented API.
  • 03Provides a Java API for embedding checks in applications.
  • 04Includes a standalone GUI and command-line version.
  • 05Offers a Wikipedia package for checking articles.
  • 06Community Docker images are available.

Use cases

  • Adding proofreading to a writing or content-editing application via the HTTP API.
  • Running a private grammar-checking server for an organization without sending text to third parties.
  • Checking documents from the command line or in a build pipeline.
  • Embedding grammar checks in a Java application.

Quick start

  1. 1

    Install Java 17 and Apache Maven

  2. 2

    Clone the repository with a shallow clone

    git clone --depth 5 https://github.com/languagetool-org/languagetool.git
  3. 3

    Build the standalone package from the project root

    ./build.sh languagetool-standalone package -DskipTests

Things to know

  • Running it requires building from source with Java 17 and Apache Maven.
  • A full clone needs more than 500 MiB of download and over 1,500 MiB of disk space.
  • The core is licensed under LGPL 2.1 or later, a copyleft license.

Topics

#grammar#spellcheck#proofreading#natural-language-processing#style-checker#java#natural-language

FAQ

What is languagetool?
Open-source grammar, spelling and style checker for English, Spanish, French, German and 20+ other languages, usable as a server, Java library or CLI. LanguageTool is open-source proofreading software that checks text for grammar, style and spelling errors in English, Spanish, French, German, Portuguese, Polish, Dutch and more than 20 other languages. It is designed to catch many mistakes that a simple spell checker cannot detect.
Is languagetool free to use? What license does it have?
languagetool is open source under the LGPL-2.1 license. Check the license terms before using it in commercial products.
Is languagetool still maintained?
Actively maintained. The last commit to languagetool was on Oct 21, 2026.
What can I use languagetool for?
Adding proofreading to a writing or content-editing application via the HTTP API. Running a private grammar-checking server for an organization without sending text to third parties. Checking documents from the command line or in a build pipeline. Embedding grammar checks in a Java application.
How do I install languagetool?
Install Java 17 and Apache Maven Clone the repository with a shallow clone: git clone --depth 5 https://github.com/languagetool-org/languagetool.git Build the standalone package from the project root: ./build.sh languagetool-standalone package -DskipTests
Where can I get languagetool?
The source code and installation instructions are on GitHub: https://github.com/languagetool-org/languagetool

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