Harper

Harper is an open-source English grammar and spell checker for developers and writers. It is designed to lint writing locally instead of sending text to a server, addressing privacy and latency concerns in server-based grammar tools.

The checker focuses on English and covers US, UK, Canadian, Australian, and Indian English. It is written in Rust, can load through WebAssembly, and is designed to lint documents in milliseconds with a small memory footprint.

Harper includes integrations for Obsidian and editor workflows through harper-ls, with support for Visual Studio Code, Neovim, Helix, Emacs, and Zed. It is open source, and its core is extensible for additional language support.