Automattic/harper

▲ 360 stars today★ 15,757⑂ 663

Offline, privacy-first grammar checker. Fast, open-source, Rust-powered

About Automattic/harper

Automattic/harper is an open-source project on GitHub, mainly written in Rust. Offline, privacy-first grammar checker. Fast, open-source, Rust-powered It currently holds 15,757 stars and 663 forks with 930 open issues, and was last pushed on 2026-09-21 (repository created 2023-10-22).

Project Overview

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GitHub Repository Details

Repository Automattic/harper · default branch master · size 43665 KB · watchers 45 · source: GitHub REST API and repository README

README

Harper

Harper Binaries Website Checks Crates.io NPM Version Downloads Obsidian Plugin Downloads

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 tedious.

LanguageTool is great, if you have gigabytes of RAM to spare and are willing to download the ~16GB n-gram dataset. Besides the memory requirements, I found LanguageTool too slow: it would take several seconds to lint even a moderate-size document.

That's why I created Harper: it is the grammar checker that fits my needs. Not only does it take milliseconds to lint a document, take less than 1/50th of LanguageTool's memory footprint, but it is also completely private.

Harper is even small enough to load via WebAssembly.

Language Support

Harper currently only supports English, but the core is extensible to support other languages, so we welcome contributions that allow for other language support.

Performance Issues

We consider long lint times bugs. If you encounter any significant performance issues, please create an issue on the topic.

If you find a fix to any performance issue, we would appreciate the contribution. Just please make sure to read our contribution guidelines first.

Links

Huge Thanks

This project would not be possible without the hard work from those who contribute.

Harper's logo was designed by Lukas Werner.

GitHub Stars & Activity

15,757Stars
663Forks
930Open issues
RustLanguage

GitHub Popularity

GitHub stars15,757
Forks663
Open issues930
Primary languageRust
LicenseApache-2.0
Stars gained today360
Created2023-10-22
Last pushed2026-09-21

Trending History

Weekly boardrank #80 · ▲ 360 stars

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