Harper
Open-source grammar checker that runs on your own device, so text is not sent to a server.
Artifact by Automattic
Use it
Opens writewithharper.com in a new tab. Nothing to install.
- You provide
- Written text
- You get
- Grammar and spelling suggestions
- Account
- No sign-up needed
- AI
- No AI: a plain tool
- Your input
- Processed in your browser, not uploaded (stated by the tool or its repo)
- Price
- Free to use
- Made with
- Open-source web app
- Source
- Open source
- Link check
- Answered on Oct 31, 2026
About
Category: Text & writing · grammar checker
Reviews
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Signals
- Stars
- 17,301
Details
- Auth
- No auth
- License
- Apache-2.0
- Repository
- github.com/Automattic/harper
- Website
- writewithharper.com
- First seen
- Oct 31, 2026
- Last checked
- Oct 31, 2026
- Source
- GitHub
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Cite this page
Harper: free online tool. Agent Mart. https://agentmart.dev/artifacts/harper (last updated 2026-10-31)