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Harper vs QuillBot: catalog facts
Harper	QuillBot
Free Free and open source.	Freemium Free to use with limits, with a Premium subscription for more.
macOS, Web, Browser extension, Command line	Windows, Android, iOS, Web, Browser extension
All checks run locally with no telemetry Works in browsers, editors and system-wide on macOS	Many writing tools in one place Extensions for Chrome, Edge and Safari
English only Rule-based checks do not rewrite text the way AI assistants do	Advanced modes need a Premium subscription Text is processed on QuillBot's servers
Downloadable app, Web application, Browser extension	Downloadable app, Web application, Browser extension
Open source	Closed source
License not stated	License not stated
Not stated if an account is needed	Not stated if an account is needed
Works offline	Needs internet
Official website Full listing and sources Checked September 26, 2026	Official website Full listing and sources Checked September 23, 2026

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