
Private Grammar Checker - Harper by Elijah Potter
ExperimentalExperimental
A private grammar checker for 21st Century English
You'll need Firefox to use this extension
Extension Metadata
Screenshots


About this extension
Harper is a fast, privacy-first grammar and spelling checker that works entirely offline. No cloud. No tracking. No ads. Just clean, real-time feedback as you write.
Harper is designed for performance and precision. It checks your grammar and spelling across websites, documents, and comment fields — without sending a single keystroke to the internet.
Who it's for:
• Writers who want accurate grammar help without giving up privacy
• Developers writing technical docs, READMEs, or blog posts
• Markdown lovers, privacy advocates, and minimalists
• Anyone tired of bloated grammar checkers and upsells
Key features:
• ✅ Grammar and spelling suggestions in real time
• 🔒 100% offline – your text never leaves your machine
• 🌎 Supports American 🇺🇸, British 🇬🇧, Canadian 🇨🇦, and Australian 🇦🇺 English
• 💻 Great for Markdown, documentation, and code comments
• 🚫 No popups, ads, or feature nags
• 🛠️ Open source – inspect and contribute on GitHub
• ⚡ Built in Rust for speed and memory efficiency
Unlike tools that harvest your data, Harper runs entirely in your browser — fast, secure, and unobtrusive. You write. Harper keeps it clean.
Harper is designed for performance and precision. It checks your grammar and spelling across websites, documents, and comment fields — without sending a single keystroke to the internet.
Who it's for:
• Writers who want accurate grammar help without giving up privacy
• Developers writing technical docs, READMEs, or blog posts
• Markdown lovers, privacy advocates, and minimalists
• Anyone tired of bloated grammar checkers and upsells
Key features:
• ✅ Grammar and spelling suggestions in real time
• 🔒 100% offline – your text never leaves your machine
• 🌎 Supports American 🇺🇸, British 🇬🇧, Canadian 🇨🇦, and Australian 🇦🇺 English
• 💻 Great for Markdown, documentation, and code comments
• 🚫 No popups, ads, or feature nags
• 🛠️ Open source – inspect and contribute on GitHub
• ⚡ Built in Rust for speed and memory efficiency
Unlike tools that harvest your data, Harper runs entirely in your browser — fast, secure, and unobtrusive. You write. Harper keeps it clean.
Rate your experience
PermissionsLearn more
This add-on needs to:
- Access browser tabs
- Access your data for all websites
More information
- Add-on Links
- Version
- 0.37.0
- Size
- 2.36 MB
- Last updated
- 3 days ago (May 21, 2025)
- Related Categories
- License
- Apache License 2.0
- Version History
Add to collection
More extensions by Elijah Potter
- There are no ratings yet
- There are no ratings yet
- There are no ratings yet
- There are no ratings yet
- There are no ratings yet
- There are no ratings yet