Harper: open-source local grammar checker undercuts Grammarly at $0 with no cloud
thisguyknowsai · x · 2026-11-10
Harper is an open-source (Apache 2.0) grammar and spell checker written in Rust, positioned as a privacy-respecting free alternative to Grammarly.
Key points:
- Runs entirely locally: no cloud round-trips, no telemetry, no LLM in the loop — your writing never leaves the device
- Suggestions in under 10ms, fast enough to keep up with typing
- Free, no subscription, no account required
Wide integration surface: Chrome/Firefox/Edge extensions, VS Code, Obsidian, Neovim (LSP), WordPress, Zed, a native macOS desktop app that works system-wide, plus a JavaScript library and Rust crate for custom integrations.
Supports custom dictionaries and grammar rules; English only. It focuses on grammar/spelling/capitalization/awkward phrasing — not AI rewriting.
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