Overview:
Harper is a grammar checker for English, designed to be fast, lightweight, and private. Unlike cloud-based services that upload text to external servers, Harper processes everything locally, allowing it to check a document in milliseconds. It was created as an alternative to tools the author found too slow or resource-intensive. Harper requires significantly less memory than comparable checkers and is small enough to run via WebAssembly, making it suitable for developers, privacy-conscious users, and anyone who needs an efficient offline grammar tool.
Core Features:
Local-only processing: All grammar checking happens on the user's machine; no text is sent to external servers.
Fast linting: Can check a document in milliseconds, with performance issues treated as bugs.
Small memory footprint: Uses less than 1/50th the memory of a comparable grammar checker like LanguageTool.
WebAssembly support: Compact enough to be loaded and run via WebAssembly.
Editor integrations: Available for Visual Studio Code, Neovim, Helix, Emacs, and Zed.
Use Cases:
Writers who value privacy: Users can check grammar without their text being sent to or processed by a third party.
Developers integrating into editors: Teams can use supported editor plugins or the
harper-lslanguage server for inline grammar checking.Self-hosters or offline users: Anyone who needs a grammar checker that does not require a network connection or large local datasets.
Performance-sensitive workflows: Writers or editors working with large documents who cannot tolerate the latency of cloud-based or heavyweight checkers.
Why It Matters:
Harper offers a private, local grammar-checking alternative to cloud-dependent services like Grammarly and resource-heavy tools like LanguageTool. By running entirely on-device with a small memory footprint and sub-second response times, it eliminates both data privacy concerns and network latency. Its editor integrations and WebAssembly support make it a practical choice for developers and writers seeking a fast, self-contained grammar checker that does not require ongoing subscription costs or external infrastructure.
