head to head · open source
Harper vs LanguageTool
Harper has 17,365 GitHub stars, 794 forks, 896 open issues and last shipped yesterday. LanguageTool has 15,229 stars, 1,598 forks, 2,148 open issues and last shipped yesterday. Harper leads on adoption by 14% (17,365 vs 15,229 stars). Harper is written in Rust under Apache-2.0; LanguageTool is written in Java under LGPL-2.1. Harper has attracted 5% as many forks as stars, LanguageTool 10%. Harper was the more recently maintained of the two, and both are self-hostable with no licence fee.
Two open source projects, one decision. Both are free and self-hostable — the differences are community size, license terms, language stack and release pace.
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Side by side
| Harper | LanguageTool | |
|---|---|---|
| GitHub stars | ★ 17K | ★ 15K |
| License | Apache-2.0 | LGPL-2.1 |
| Written in | Rust | Java |
| Last push | 2026-11-02 | 2026-11-02 |
| Forks | ⑂ 794 | ⑂ 1.6K |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick Harper if
- You weight community size — 17K stars and counting
- You want the Apache-2.0 license terms
- Your stack matches Rust
- You value the larger contributor base for long-term maintenance
pick LanguageTool if
- You want the LanguageTool feature set and don't need the biggest community
- You prefer the LGPL-2.1 license terms
- Your stack matches Java
- You evaluated both and LanguageTool fits your workflow better
About Harper
Harper Harper is an English grammar checker designed to be just right. I created it after years of dealing with the shortcomings of the competition. Grammarly was too expensive and too overbearing. Its suggestions lacked context, and were often just plain wrong . Not to mention: it's a privacy nightmare. Everything you write with Grammarly is sent to their servers. Their privacy policy claims they don't sell the data, but that doesn't mean they don't use it to train large language models and god knows what else. Not only that, but the round trip time of the network request makes revising your work all the more…
read the full Harper overview →
About LanguageTool
LanguageTool LanguageTool is open source proofreading software for English, Spanish, French, German, Portuguese, Polish, Dutch, and more than 20 other languages. It finds many errors that a simple spell checker cannot detect. LanguageTool Forum How to run your own LanguageTool server HTTP API documentation How to use our public server via HTTP How to use LanguageTool from Java (Javadoc) For more information, please see our homepage, at languagetool.org , this README , and CHANGES . The LanguageTool core (this repo) is freely available under the LGPL 2.1 or later. Docker Try one of the following projects for a…
read the full LanguageTool overview →
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Frequently asked questions
Is Harper or LanguageTool more popular?
Harper has 17,365 GitHub stars and LanguageTool has 15,229. Harper has the larger community by that measure.
Are Harper and LanguageTool free?
Both are open source. Harper is licensed under Apache-2.0 and LanguageTool under LGPL-2.1. Neither carries a licence fee.
What is the difference between Harper and LanguageTool?
Harper is written in Rust and LanguageTool in Java. The practical differences are community size, licence terms, language stack and release cadence — all compared in the table above.
Which should I choose, Harper or LanguageTool?
Choose Harper if you want the larger community (17,365 stars) or its Apache-2.0 licence terms. Choose LanguageTool if its feature set, stack or LGPL-2.1 licence fits better. Both are self-hostable.