You can use LanguageTool locally in three different ways: its desktop app for offline writing checks, its standalone Java application or command-line tool for local text, or an embedded HTTP server for compatible integrations. Choose the desktop app for straightforward offline use; the server is a separate, advanced setup with important feature and access limits.
Which local LanguageTool option fits your needs?
| What you want to do | Best-fit route | What to know |
|---|---|---|
| Check writing offline on a Windows or Mac computer | LanguageTool desktop app | LanguageTool’s help center says the desktop app can check writing without an internet connection. This is distinct from hosting a server yourself. LanguageTool help center |
| Check a local text file or run the checker as a standalone Java application | Standalone app or command line | The standalone README documents launching the application and checking a file. Its version 6.6 instructions require Java 17 or later. LanguageTool standalone README |
| Let another compatible application send text to a local checker | Embedded HTTP server | This takes command-line setup and has integration and feature constraints. LanguageTool embedded HTTP server guide |
| Embed LanguageTool directly inside a Java program | Java API | LanguageTool recommends its HTTP server instead of direct Java API use. LanguageTool Java API documentation |
These routes are not interchangeable. The desktop app is the simple offline choice; standalone and CLI suit local files or automation; a server is useful when another compatible tool needs a local endpoint.
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Use the desktop app for offline writing checks
For ordinary desktop use on Windows or macOS, install the LanguageTool desktop app and use it to check text without an internet connection. The help center identifies those desktop platforms and offline checking; it does not make the desktop app equivalent to the self-hosted HTTP server.
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If your goal is to let a separate application call a local LanguageTool service, use the server route below instead. In particular, the embedded-server guide says the Windows desktop app does not work with that server approach.
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Check a local text file with the standalone or command-line version
The standalone README labels its instructions as version 6.6, dated 2025-03-27. For that version, it specifies Java 17 or later. Requirements can vary by release, so check the README for the version you actually download rather than assuming this requirement applies to every release.
Launch the standalone application
With Java available, the version 6.6 README gives either of these launch methods:
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Check a text file from the command line
The documented pattern is java -jar languagetool-commandline.jar -l xx <filename>. Replace xx with a language code such as en-US, and replace <filename> with the path to your text file. For example, the structure is:
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Run a local HTTP server for compatible integrations
The embedded server lets a compatible application send text to a LanguageTool service running on your computer. LanguageTool’s guide explicitly describes this as an advanced command-line setup, not a one-click replacement for the desktop app.
Start the server and test the local endpoint
- Download and unpack a recent
LanguageTool-latest-snapshot.zip, following the current instructions in the official embedded HTTP server guide. - Start the included server from the command line as described in that guide. The documentation shows the local check endpoint as
http://localhost:8081/v2/check. - Use HTTP POST for requests beyond a basic test, as the guide recommends. Configure the application that will send text to use the local endpoint.
The guide also describes a Homebrew installation path for macOS, while noting that Homebrew support is not provided by the LanguageTool team. Follow the guide’s current commands for the installation method you choose.
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Understand the server’s limits before relying on it
- The documented snapshot provides a basic server without AI-based rules. Do not assume it has the same features as a hosted or desktop experience.
- The Windows desktop app does not work with this server approach.
- The server is not accessible from other hosts by default. The guide says remote use requires the
--publicoption; do not enable network access casually. Only expose a service when you understand the network setting and have an appropriate deployment design. - The guide describes connecting a browser add-on through an experimental local-server setting, but that does not establish compatibility for every add-on or application. Check the add-on’s current settings and compatibility.
- For Safari, the guide says HTTPS and a reverse proxy are required for this setup.
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These constraints matter if you are choosing a local server for privacy or offline use: running the checker locally does not automatically provide every feature or integration available elsewhere.
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When does the Java API make sense?
If you are building a Java application, LanguageTool documents Maven and Gradle dependencies and language-specific artifacts. Its developer documentation nevertheless recommends the HTTP server rather than embedding the Java API directly: Embedding LanguageTool in Java applications.
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The documentation explains that using a server can reduce CPU, memory, and disk use in the application process, particularly when n-gram data is involved. This is the project’s rationale, not a measured performance guarantee for your computer. The Java API page says Java 17 has been required since LanguageTool version 6.6.
What “local” does—and does not—guarantee
LanguageTool describes its project as open source under LGPL 2.1 or later and as supporting more than 25 languages: LanguageTool project repository. Those project-level facts do not establish identical features across the desktop app, standalone checker, server, and integrations. Select the route whose documented behavior matches your use case, and check version-matched instructions before installing or exposing a service.
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