Overview:
LanguageTool is an open-source proofreading software that supports English, Spanish, French, German, Portuguese, Polish, and over 20 other languages. It detects grammar, style, and spelling errors that simple spell checkers cannot identify. It is designed for writers, editors, and developers who need a language-checking tool that can be self-hosted or accessed via an HTTP API. The core project is available under the LGPL 2.1 license.
Core Features:
Multi-language support: Checks text in more than 20 languages, including major European languages.
Advanced error detection: Finds grammar, style, and spelling errors beyond basic spell checking.
HTTP API: Provides a documented API for integrating LanguageTool into other applications or workflows.
Self-hosting: Offers instructions for running a private LanguageTool server, giving users control over data and processing.
Java API (Javadoc): Supports direct integration from Java applications for developers.
Community Docker images: Multiple community-maintained Docker configurations are available for containerized deployment.
Use Cases:
Developers integrating proofreading: Using the HTTP API to add grammar and style checking to web apps, editors, or content management systems.
Self-hosters running a private server: Deploying LanguageTool on their own infrastructure for data privacy or offline use.
Writers and editors checking multilingual text: Using the desktop application or server to proofread content in over 20 languages.
Building custom rule sets: Contributing error detection rules to extend LanguageTool's capabilities for specific use cases.
Why It Matters:
LanguageTool provides a transparent, self-hostable alternative to proprietary grammar and style checkers. Its open-source nature allows users to inspect, modify, and extend the detection rules. The project focuses on a core utility—advanced proofreading—without bundling unrelated features, making it a focused tool for developers and self-hosters who want control over their language-checking pipeline.
