Correctly vs Harper
Correctly
iamaamir.github.io
Harper
writewithharper.comSide by side
| Figure | Correctly | Harper |
|---|---|---|
| Price from | Free | Free |
| Free plan | Yes | Yes |
| Free trial | — | — |
| Open source | — | Yes |
| Web | — | Yes |
| Windows | — | Yes |
| macOS | — | Yes |
| Linux | — | Yes |
| iOS | — | Yes |
| Android | — | Yes |
| API | — | Yes |
| Plans published | 1 | 2 |
| Spec score · AI Grammar Checkers | 8.0 (#18) | 8.8 (#7) |
| Spec score · Grammar checkers | 7.4 (#79) | 8.9 (#19) |
| Browser extension | Yes | Yes |
| Integrations | The maker names Groq, OpenRouter, and DeepSeek as examples of OpenAI-compatible services. | The maker lists browser and editor extensions, a language server, a JavaScript library, a Rust crate, and native apps. |
| Languages | The README says English is currently supported, with more languages coming. | Harper supports English and British, American, Canadian, Australian, and Indian dialects of English. |
| License | Correctly is open source under the BSD 3-Clause License. | The source code is released under the Apache License 2.0. |
| Privacy | The maker says there is no Correctly cloud or account, and that text is processed locally or sent directly to the provider the user configures. | Checks run locally; the maker says Harper has no cloud round-trips, telemetry, or LLM in the loop. |
| What it does | Correctly checks writing in place for grammar, spelling, and punctuation using AI. | Harper is an English grammar checker that detects spelling, capitalization, phrasing and grammar problems locally on the device. |
Plans
In their own words
Correctly
Correctly has no write-up on Specifiction yet; its figures are above.
Harper
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.