Harper

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Harper is an open-source, privacy-first grammar checker that operates offline. Powered by Rust, it offers fast and accurate grammar checks without sending data to external servers.

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At a glance

Pricing

Open Source

Free tier

Yes

API

Skill level

Technical

About

What is harper?

Harper is an English grammar checker designed for speed, privacy, and accuracy. Unlike many competitors, it operates entirely offline, ensuring that everything you write remains private and is not sent to external servers or used to train large language models. Built with Rust, Harper boasts significantly faster linting times and a smaller memory footprint compared to alternatives like LanguageTool. It is also small enough to load via WebAssembly, making it highly efficient. Currently, Harper supports English, but its core is extensible for other languages, welcoming community contributions. The project emphasizes performance, treating long lint times as bugs and encouraging users to report or fix any performance issues they encounter.

Best used for

Ideal for writers who need to quickly proofread documents, ensure their writing remains private, and integrate a grammar checker directly into their preferred editor. Especially valuable for those concerned about data privacy and seeking a high-performance, offline solution.

Common actions

check grammar

proofread text

ensure privacy

edit documents

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Capabilities

Key features

Offline grammar checking
Privacy-first design
Rust-powered performance
Low memory footprint
WebAssembly compatible
Open-source

Target Audience

writer

Integrations

visual-studio-codeneovimemacshelixzedobsidian

Pricing & Plans

Open Source

Free

FAQs

What makes Harper different from other grammar checkers like Grammarly or LanguageTool?

Harper distinguishes itself by being offline, privacy-first, and open-source. Unlike Grammarly, it doesn't send your data to servers, and compared to LanguageTool, it boasts significantly faster performance and a much smaller memory footprint, making it highly efficient for quick checks.

Does Harper support languages other than English?

Currently, Harper primarily supports English. However, its core architecture is designed to be extensible for other languages. The project welcomes contributions from the community to expand its language support in the future.

Can Harper be integrated into my existing writing workflow?

Yes, Harper offers integrations with several popular editors. Official documentation is available for Visual Studio Code, Neovim, Helix, Emacs, and Zed, allowing you to seamlessly incorporate Harper's grammar checking capabilities into your preferred development or writing environment.

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