What it is
Harper checks English text for grammar, spelling, and style problems entirely on your own machine, with no text sent to a server. It ships as a language server (harper-ls) for editors like VS Code, Neovim, Helix, Emacs, and Zed, a JavaScript/WebAssembly package (harper.js), a browser extension, and an Obsidian plugin. Writers and developers who want quick proofreading without a cloud subscription or a heavy memory footprint can drop it into the tools they already use.