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Grammarly vs Harper: catalog facts
Grammarly	Harper
Freemium Free to sign up, with paid plans for more features.	Free Free and open source.
Web, Browser extension	macOS, Web, Browser extension, Command line
Grammar, spelling and clarity checks as you type One-click paragraph rewrites and tone suggestions	All checks run locally with no telemetry Works in browsers, editors and system-wide on macOS
Requires an account Text is processed on Grammarly's servers	English only Rule-based checks do not rewrite text the way AI assistants do
Hosted service, Browser extension	Downloadable app, Web application, Browser extension
Closed source	Open source
License not stated	License not stated
Account needed	Not stated if an account is needed
Not stated if it works offline	Works offline
Official website Full listing and sources Checked September 23, 2026	Official website Full listing and sources Checked September 26, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.