LanguageTool

LanguageTool catches the mistakes a spell checker cannot see, the ones that need grammar and style rules instead of a dictionary lookup. It covers English, Spanish, French, German, Portuguese, Polish and Dutch, plus more than twenty other languages.

The core in this repository is a Java library, usable in three shapes: called directly through the Java API, run as an HTTP server of your own, or reached through the project's public server for light use. Detection rules come from contributors, and the development documentation explains how to write new ones.

Installation offers several routes depending on what you want.

• Install script: a shell script installs or builds, with flags for a quiet run, a chosen package and clean removal.
• Packages: standalone, Wikipedia and an office extension for LibreOffice and OpenOffice build separately.
• Run modes: the same install runs as a graphical app, a command line checker or a server.
• Docker: no official image, though three community-maintained ones are listed.
• Building: Java 17 and Maven, with a shallow clone advised since a full one pulls more than 500 MiB.

The core is distributed under LGPL 2.1 or later. Running your own instance is the point for anyone who cannot send drafts to a third party, and the HTTP API is documented the same way for a private server and the public one, so an editor integration written against either keeps working.