Automattic/harper

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

RustApache-2.0 Last commit 22 hours ago writewithharper.com

Updated 34 min ago

Open on GitHub

Last 24 hours: +85; stars
Last 7 days: +528; stars
Last 30 days: +1.2k; stars
Total stars: 16,889
Forks: 855

Star history

Total stars at the end of each week, from GitHub’s daily star counts.

Why it’s rising: +528 stars this week, against ~197 in a usual week

Rank in its topics

Out of repos that gained at least 20 stars in the period

Rank of Automattic/harper in each topic for today, this week and this month
Topic	Today	This week	This month
Browser extensions topic	#8of 10	#14of 51	#24of 98
WebAssembly topic	#4of 6	#15of 44	#17of 94
Privacy topic	#10of 24	#25of 119	#48of 206
Web frameworks topic	#36of 79	#79of 288	#126of 475
JavaScript topic	#102of 171	#185of 497	#230of 755
Rust topic	#94of 147	#203of 541	#257of 772

Health signals

HealthyChecked Oct 14, 2026

Commit activity: Commits in 13 of the last 13 weeks 326 commits on the default branch in 90 days
Maintainers: 12 commit authors in 90 days Top author: 48% of the last 89 commits
Issue responsiveness: Median first response: 5 days 5 of the latest 50 issues opened in 90 days are closed
Pull requests: 32 merged, 1 closed, 17 open Of the latest 50 opened in 90 days
Releases: Last release: 2 weeks ago 36 releases in the last 12 months
Project hygiene: License, CI; no security policy
OpenSSF Scorecard: Not scanned Unknown, not counted against the project

Signals are computed automatically from public GitHub data. They are not an endorsement or a security audit. How health is computed

README

README.md

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 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.