Last checked October 15, 2026

Harper

Harper is a Rust grammar checker that runs locally in editors and a browser extension. Nothing is sent to a server. It is younger and narrower than Grammarly or LanguageTool, and that is the point.

Open sourceApache-2.0WritersDevelopersPrivacy-conscious

MacWindowsLinuxWeb

Website·Source

Free tier

The checker is free and local.

Hosted

No hosted price recorded.

Self-host

Easy. It runs on the device. There is no server cost. About $0.

Drop-in scores

Replacing Grammarly100% of the checklist checked.

Sources checked

https://github.com/Automattic/harper