dev.languagetool.org

LanguageTool embedded HTTP Server

LanguageTool comes with its own embedded HTTP server, so you can send a text to a local instance of LanguageTool. This page describes how to set this up.

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 (>200MB) and unzip it.

Please note:

This will give you a basic LanguageTool server without AI-based rules. The AI-based rules are only available in the Cloud.
The Windows desktop app will not work with this approach.

On MacOS you can install the server using brew (please note that Homebrew support is not provided by the LanguageTool team):

brew install languagetool

Starting from Command Line

The next three steps are optional but strongly recommended on Linux and Mac for good language detection - on Windows, fastText is not available and LanguageTool’s language detection will not work that well:

Build fastText
Download the fastText language identification model
Create a file server.properties with this content (change /path/to/fasttext to your fastText installation):
```
fasttextModel=/path/to/fasttext/lid.176.bin
fasttextBinary=/path/to/fasttext/fasttext
```

If you skip these steps, create an empty server.properties file instead.

On the command line, go to the unzipped LanguageTool directory and start the LanguageTool HTTP server using these commands:

java -cp languagetool-server.jar org.languagetool.server.HTTPServer --config server.properties --port 8081 --allow-origin

Or this command that is useful for system package management installs like for Arch Linux:

languagetool --http --config server.properties --port 8081 --allow-origin "*"

On MacOS you can start the server as a service in the background using brew:

brew services start languagetool

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 now 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 that Safari seems to require https, so you’d need to set up a reverse proxy and configure https://localhost:8082/v2 as “Other server” (source). Note: The LanguageTool server doesn’t support synonyms, so the synonym feature in the add-on will not work.

Testing the server

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

http://localhost:8081/v2/check?language=en-US&text=my+text

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

curl -d "language=en-US" -d "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.

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.

Using SSL/TLS

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

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