harper

Project Overview

Harper is a free, open-source, privacy-first grammar checker that runs entirely on-device with no cloud round-trips, no telemetry, and sub-10ms suggestions. Maintained by Automattic.

Key Features

• Completely offline grammar checking
• Zero privacy violation – doesn't ship your writing over the internet
• Language Server Protocol (LSP) support
• Sub-10ms response time
• Portable pre-built binaries available

Target Audience

• Writers who need privacy protection
• Developers integrating into editors
• Users who don't want their writing uploaded to the cloud

Quick Start

1. Download portable pre-built binaries from GitHub Releases
2. Or install via winget install --id=Automattic.harper-ls -e
3. Configure your editor to use the Harper LSP
4. Start writing – Harper provides grammar suggestions in real time

Core Advantages

• Completely offline with privacy-first
• Fast response (<10ms)
• LSP support for integration with any editor
• Maintained by Automattic for reliable quality

System Requirements

• OS: Cross-platform (Windows, macOS, Linux)
• Architectures: x86_64, arm64
• Additional Dependencies: None

Notes

• The LSP frontend is harper-ls
• Portable binaries can be used without installation