LanguageTool
Self hosted proofreading server for grammar, spelling, punctuation, and style checks across many languages, with a local HTTP API
Quick Start
java -cp languagetool-server.jar org.languagetool.server.HTTPServer --config server.properties --port 8081 --allow-origin Overview
LanguageTool is a self hosted proofreading engine for spelling, grammar, punctuation, and style checks across more than 25 languages. LanguageTool is best known as a browser and writing assistant, but the open source core also includes an embedded HTTP server that you can run locally for private text checking, internal writing tools, editor integrations, and custom apps.
The self hosted server is useful when drafts, support replies, legal notes, or internal docs should not pass through a hosted writing service. You send text to the local /v2/check API and get structured suggestions back, including rule IDs, explanations, offsets, and replacement text. It is not trying to be a full AI writing app. The local version is mainly rule based proofreading, while AI based rules and some premium features stay with the hosted LanguageTool service.
Setup is more technical than a typical one click web app. The official path uses Java and the LanguageTool server JAR, while Docker users rely on community maintained images. If you expose it beyond localhost, add authentication at the reverse proxy because the server itself does not provide user accounts. For teams that care about private proofreading, LanguageTool is mature, active, and much easier to trust than most newer writing assistants.
LanguageTool: Pros & Cons
| Pros (The Wins) | Cons (The Friction) |
|---|---|
| Privacy: Run checks locally Keep drafts off cloud APIs. | Cloud Gap: AI based rules stay hosted only. |
| Maturity: Long running project with active commits. | Docker: Images are community maintained, not official. |
| Integrations: HTTP API works with editors and custom apps. | Access Control: Public servers need reverse proxy auth. |
| Language Coverage: Checks many languages from one local service. | Setup: Java server path suits technical users. |
Use Cases
Specific ways to use LanguageTool for your workflow.
Deployment Strategy
Recommended ways to host LanguageTool in your own environment.