Free Grammar Checker
Grammar Checker finds spelling, grammar, punctuation, capitalization, style and repetition issues in English text and suggests fixes you apply with one click. It runs the open-source Harper engine on your device, supports American, British, Canadian, Australian and Indian spelling, and loads about 16 MB on first use, which your browser then caches.
- Engine:
- Harper (WebAssembly)
- Dialects:
- US, UK, Canadian, Australian, Indian
- Download:
- About 16 MB on first use, then cached
- Price:
- Free
- Runs:
- Locally, in your browser
- Uploads:
- None: files never leave your device
- Account:
- Not needed
Quick answers
Is my text sent to a server?
No. The grammar engine (Harper) runs inside your browser as WebAssembly, so your text never leaves your device and keeps working offline after the first load.
Which languages are supported?
English only: American, British, Canadian, Australian and Indian spelling. Text in other languages will show many false spelling errors.
Processed on your device: your files are never uploaded. How it works
Network activity in this tab
What this page has requested since you opened the site in this tab. An upload is any request that sends data: POST, PUT, PATCH or a request with a body.
No uploads: nothing has been sent from this page.
No network requests yet.
To see every request, open your browser's developer tools (Network tab).
How to use the Grammar Checker
- Type or paste your English text (or open a .txt/.md file); the checker loads once and then checks as you type.
- Underlines show issues by color: click one, or pick it in the list, to see suggestions.
- Apply a suggestion, ignore it, add the word to your dictionary or turn the check off; use Fix all for clear-cut fixes.
- Copy or download the corrected text.
Credits & open source
Our own code plus open-source libraries. Thank you to the people who make these projects.
- HarperPrivate English grammar checker compiled to WebAssembly. © Elijah Potter and Automattic · Apache-2.0
- fflateFast ZIP compression for batch downloads. © Arjun Barrett · MIT
Web platform APIs used: Web Workers, localStorage, Clipboard API, File API, Intl.Segmenter, URL API.
Full license texts: third-party notices · all credits
Frequently asked questions
Why is the first load slower?
The checker downloads its dictionary and rules (about 16 MB) once. Your browser caches them, so later visits start quickly.
What does “Fix all” change?
Only issues with a single, clear suggestion, such as repeated words or a missing space. Spelling with several candidates is left for you. Press Ctrl+Z in the text to undo.
How do I stop a word being flagged?
Choose “Add to dictionary” on the issue, or add words in Personal dictionary. The list is saved in this browser.