Harper
An offline, privacy-first English grammar checker written in Rust, built to lint documents in milliseconds with a small memory footprint and integrations for popular code editors.
Harper is an English grammar checker built to run entirely offline, so text never leaves the user's machine. It was created as a faster, lighter alternative to existing checkers, aiming to lint even large documents in milliseconds while using a small fraction of the memory such tools typically need.
Harper currently supports English only, though its core is designed to be extensible to other languages. It is small enough to run via WebAssembly, and ships integrations for editors including Visual Studio Code, Neovim, Helix, Emacs and Zed, plus a harper-ls language server and a harper.js package.
The project is written in Rust and is open source.