Duden-Mentor vs Harper

Duden-Mentor checks German text for spelling, grammar, punctuation, and style, then suggests corrections. It can flag filler words, repeated wording, and overly long sentences, with suggestions for readability. The service supports German variants for Germany, Austria, and Switzerland, but checks German only. Browser extensions are available for Chrome, Firefox, and Microsoft Edge, and the plug-in works in text fields on services including Gmail, Web.de, GMX.de, Trello, Facebook, and WordPress. A Microsoft Word add-in supports macOS from Word 2016 and Windows from Word 2019. An internet connection is required. Duden says text is encrypted in transit, not used for AI training, and deleted after checking. Basis is free and lists a 10-word personal dictionary and 500 characters without an account. Pur costs €2.99 a month, billed 35,88 € pro Jahr, with 10 test corrections or rewrites monthly. Premium costs €7.95 a month, billed 95,40 € pro Jahr, with 250 monthly text optimizations; Premium Plus costs €9.95 a month, billed 119,40 € pro Jahr, with unlimited optimizations. Paid plans are annually payable and annually cancellable.

Harper is a free, open-source grammar checker that flags capitalization, spelling, awkward phrasing, and grammar errors. The maker says checks run locally, with no cloud round-trips, telemetry, or LLM in the loop, and that suggestions appear in under 10 ms. Harper is available through browser and editor extensions, a language server, a JavaScript library, a Rust crate, and native apps. Listed integrations include Chrome, Brave, Edge, Firefox, VS Code, Cursor, Obsidian, WordPress, Neovim, Zed, Helix, Emacs, and Sublime Text. Its language support covers English and British, American, Canadian, Australian, and Indian English dialects. Harper Desktop lets users toggle rules, add dictionary entries, select a dialect, and turn checking on or off per app. The desktop app is labeled beta for macOS 14 or later, and the Windows desktop app is also described as a beta; its binary was not signed at the time of the listed post. Harper is free, with no account or credit card required.