Automattic/harper

Health v2 · maintenance only

Adoption not part of the score

14744 stars · 583 forks observed · 2026-08-28

What it is AI-extracted, prompt v1, taxonomy v1, 2026-08-29, confidence not recorded

Harper is an open-source, offline English grammar checker written in Rust that runs entirely on-device with millisecond lint times. It ships as a language server, JavaScript/Rust libraries, browser and editor extensions, and native apps, with no cloud calls or telemetry.

Use cases

• check grammar in my writing without sending text to the cloud
• grammarly alternative that works offline
• add grammar checking to my obsidian vault
• lint markdown documents in neovim for grammar mistakes
• embed a grammar checker in a web app via javascript
• fast spell and grammar checking in vscode or zed
• system-wide grammar checking on macos

When to choose

• you need privacy-first, fully offline grammar checking
• you want millisecond-speed linting with a tiny memory footprint
• you write in English across editors like Neovim, VS Code, Zed, or Obsidian
• you want to embed grammar checking in a Node, Bun, browser, or Rust project

When to avoid

• you need grammar checking for languages other than English
• you rely on the deep contextual suggestions of an LLM-powered checker
• you need the broad language coverage of LanguageTool

Facets

library · maturity active

nlp linter sdk plugin-system developer-tools text-editors rust wasm browser cross-platform editor-plugin browser-extension grammar-checker language-server offline privacy-first spell-check writing-assistant obsidian-plugin chrome-extension lsp natural-language-processing nodejs macos

Member repositories

For agents

markdown · JSON · MCP: product_card(name="Automattic/harper")