LanguageTool embedded HTTP Server

LanguageTool comes with its own embedded HTTP server, so you can send a text to LanguageTool via HTTP and get the detected errors back as JSON. This embedded server can be started like this.

WARNING: This approach is only supposed to be used by advanced users who are familiar with using the command line. If you’re not, we recommend using the default settings, which use our Cloud servers.

Getting the server

Download the LanguageTool Desktop version for offline use (>170MB) and unzip it.

Starting from Command Line

On the command line, go to the unzipped directory and start LanguageTool using this command:

java -cp languagetool-server.jar org.languagetool.server.HTTPServer --port 8081 --allow-origin "*"

If this fails with an error saying that java cannot be found, install Java 8 or later first.

You can remove --allow-origin "*" if you do not want to use the server from the browser add-on. You need to set this server in the browser add-on: visit the add-on’s options by clicking the cog icon, then open “Experimental settings” and select “Local server”.

NOTE: This will give you a basic server missing some statistics rules. See here for how to set up those.

Testing the server

You can test the server by calling this URL in your browser:


If you’re not just testing, you should use HTTP POST to transfer your data. You can test it like this, using curl:

curl --data "language=en-US&text=a simple test" http://localhost:8081/v2/check

You can specify a file with advanced configuration options for the LT server with --config. Use --help to get information about the supported settings in that file.

For security reasons, the server will not be accessible from other hosts. If you want to run a server for remote users, use the --public option.

Starting from stand-alone LT

Start the stand-alone application and configure it (File -> Options…) to listen on a port that is not used yet (the default port, 8081, should often be okay). This way LanguageTool will also be available in server mode until you stop it.

HTTP Parameters and Result

See the JSON API.

Note that for a server started from a GUI, a user may configure it in the configuration dialog box to disable some unwanted rules. This may be beneficial if the calling program does not allow configuration of the call to the LanguageTool server, and the user wants to enable or disable some checks. However, if the program does disable or enable any rules, then the configuration set by the user will be silently ignored.


We recommend using the HTTP server of LanguageTool and run it behind an Apache or nginx reverse proxy with SSL/TLS support.