Browser Extension
A free, open-source grammar checker that runs entirely on your device.
Rating
4.5 / 5
Pricing
Free
Difficulty
Beginner
Works on
Chrome, Firefox, macOS
Built with love by Shushant Lakhyani. Building bestproductivityresources.com
Harper is a private grammar checker for English that runs on your own machine, with no cloud round-trips, telemetry or large language model, so your writing never leaves your device. It is free and open source under the Apache 2.0 licence. Harper was created by Elijah Potter, who now builds it at Automattic. It is available as a desktop app for macOS, browser extensions for Chrome, Edge and Firefox, and plugins for VS Code, Neovim, Zed, Obsidian and WordPress. It currently supports English only, including British, American, Canadian, Australian and Indian English.
Privacy-minded writers and developers who want fast, local grammar checks.
People who write in languages other than English.
Not sold on Harper? These do a similar job, and each card says what it has in common.
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Focus: slides, markdown and presentations. Shares open source with Harper. A desktop app, not a browser extension. Adds Windows and Linux. Same 4.5 rating.
Focus: readability, editing and plain english. Shares grammarly alternative with Harper. A web app, not a browser extension. Freemium (Harper: Free). Adds Web and Windows. Rated 4.4 (Harper: 4.5).
Focus: russian, writing and ai agents. Shares open source with Harper. An AI tool, not a browser extension. Rated 4.4 (Harper: 4.5).
Want to spend nothing? These free picks cover similar ground.
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Focus: file sharing, tor and security. Shares privacy and open source with Harper. A desktop app, not a browser extension. Adds Windows and Linux. Same 4.5 rating.
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