# LanguageTool

> LanguageTool checks grammar, spelling and style in English, Spanish, French, German, Portuguese, Polish, Dutch and 20+ other languages. The open-source core (LGPL-2.1+, latest tag v6.8) runs as a Java command-line tool, desktop GUI or local HTTP server that editor plugins can point at. A self-hosted server has no AI-based rules (cloud only) and no synonyms; Premium, the hosted service and the browser add-on are separate. Optional ~8GB n-gram data improves confusable-word checks. No AI rewriting or plagiarism check.

- Repository: https://github.com/languagetool-org/languagetool
- Official docs: https://dev.languagetool.org/http-server
- Checked: 2026-10-15

## What it replaces
- Grammarly: Grammar and spelling checks, Style and clarity suggestions (partial). Rule-based grammar, spelling and style checks in many languages; no AI rewrite, tone changes or plagiarism check when self-hosted.

## Facts, with sources

| Question | Status | Answer | Source | Checked |
|---|---|---|---|---|
| Runs on my machine? | Confirmed | Yes, as a local Java server, CLI or desktop GUI; the hosted cloud service is separate | https://dev.languagetool.org/http-server | 2026-10-15 |
| Code licence | Partial | LGPL-2.1 or later (the core in this repo); Premium is not open source | https://github.com/languagetool-org/languagetool#readme | 2026-10-15 |
| Model weights licence | Confirmed | No separate model weights in the open-source core; AI-based rules exist only in the cloud service | https://dev.languagetool.org/http-server | 2026-10-15 |
| Commercial use | Partial | Yes, LGPL conditions apply if you modify and distribute the core | https://github.com/languagetool-org/languagetool/blob/master/COPYING.txt | 2026-10-15 |
| Paid services needed? | Partial | None required to self-host; AI-based rules and Premium features are paid cloud extras | https://dev.languagetool.org/http-server | 2026-10-15 |
| Hardware | Partial | Needs Java; optional n-gram data is ~8GB and should sit on an SSD; RAM needs not documented | https://dev.languagetool.org/finding-errors-using-n-gram-data | 2026-10-15 |
| Operating systems | Confirmed | Java app for Linux, macOS (Homebrew) and Windows; on Windows fastText language detection is unavailable | https://dev.languagetool.org/http-server | 2026-10-15 |
| Setup effort | Confirmed | Medium; unzip the snapshot and start the server with Java, or use a community Docker image | https://dev.languagetool.org/http-server | 2026-10-15 |

GitHub: 15142 stars, 1587 forks, last push 2026-10-16, archived: no.
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Source: RepoQuarry (https://repoquarry.dev/projects/languagetool). Data licence: CC BY 4.0. Quotes are from project documentation and belong to their authors.