Harper: Free, Open Source Grammar Checker

Founded by Elijah Potter

Check grammar and spelling locally on your computer across browsers and code editors

Pricing model

Free

Rating

★ People love it

Time to value

Immediate

You can use Harper to check grammar, spelling, and phrasing directly on your device without sending any text to external cloud servers. It catches improper capitalization, typos, and awkward wording as you type across various applications. Because it operates entirely offline using a local language engine, your writing remains completely private. You can integrate Harper into web browsers, text editors like Obsidian and WordPress, or code editors such as VS Code and Neovim to proofread documentation, code comments, markdown files, and articles in real time.

What Harper: Free, Open Source Grammar Checker does

Highlight spelling mistakes in real timeDetect awkward phrasing and suggest clearer wordingCatch improper word capitalization and punctuation errorsProofread Markdown documentation and notesCheck source code comments for grammatical errorsSwitch between British, American, Canadian, and Australian English dialectsRuns entirely on-device without cloud connections or telemetryDelivers spelling and grammar corrections in under ten millisecondsWorks inside code editors via a native Language Server ProtocolSupports multiple English dialects including American, British, Canadian, and AustralianIntegrates directly into browser text fields through browser extensionsProvides a dedicated Obsidian vault plugin for local note editingChecks spelling in code comments across numerous programming languagesAvailable as a reusable Rust crate and JavaScript library

Pricing breakdown

Pricing model: Free

PlanList price

FreeFree

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