CRX id
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Description from extension meta
The private grammar checker for 21st Century English
Image from store
Description from store
Meet Harper, the grammar-savvy sidekick that never snitches on your prose. I built Harper because I was sick of the false choice between data-hungry cloud tools and sloth-like offline checkers. Harper threads the needle—fast, lightweight, utterly private—so you can polish every clause without surrendering a single keystroke.
• Instant insight, zero latency: suggestions surface the moment you type, no spinners, no lag
• Stone-cold privacy: Harper lives entirely in your browser; your words never leave your machine
• Fluent in four dialects: American 🇺🇸, British 🇬🇧, Canadian 🇨🇦, and Australian 🇦🇺 English
• Markdown-friendly and developer-approved: flags slip-ups in READMEs, code comments, and docs without mangling syntax
• Clutter-free experience: no pop-ups, no subscription nags, no “premium” ransom notes—just quiet competence
• Open source, Rust-powered: inspect the code, fork it, or tweak it to match your workflow
• Ideal for writers who crave precision without paying a privacy tax
• Perfect for developers curating crystal-clear technical documentation
• A haven for minimalists who’d rather write than swat away ads
• Salvation for anyone fed up with bloated grammar behemoths
Install the extension and keep writing—Harper parses each sentence locally, flags awkward phrasing and rogue typos, then slips back into the shadows. No cloud pings, no data lakes—just you and your words, refined.
Latest reviews
- (2025-06-24) Steven Hubert: Doesn't work with any MSFT product, Excel, Outlook, etc.. Basically anywhere you would actually need to use it.
- (2025-06-22) Martin Caminoa Lizarralde: Harper related files in TypeScript are requested regardless if I disable it on a specific website. Missing many rules, e.g. misuse of verb tenses e.g. use of relating or related does not make a difference in a sentence, misuse or overusing of pronouns, it's good to detect some typos though. Also it misses an editor for cases on which the extension doesn't work in an input field.
- (2025-06-15) Daniel: Does not work in Google Documents, but LanguageTool does it
- (2025-05-24) imbolc: I've been using Harper in Neovim for a long time and am glad to see it as an extension!
- (2025-05-12) Filip Cujanovic: Awesome extension! It's privacy focused, that means that every check it done locally on your computer, there is no server where your data goes! And because of that it's blazingly fast compared to Grammarly.
- (2025-05-02) Notname Notname: Harper is the privacy-focused grammar checker the world needs! I've been incredibly frustrated with overbearing suggestions from alternatives like Grammarly and concerned about their privacy policy. I've been using Harper on my notes in Obsidian for months, and it's been a game-changer! I'm so happy that it's available for the browser!
- (2025-05-02) Justin Liu: It works great!