Harper
An open-source grammar and spell checker that runs entirely on your own device.
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1 more ways to get Harper
Package managers
- Homebrew
brew install harper
About Harper
Harper is a free, open-source grammar checker that it presents as a private alternative to Grammarly. It catches capitalization errors, misspellings, awkward phrasing and broken grammar in US, UK, Canadian, Australian and Indian English. All checks run locally, with no cloud requests, no telemetry and no LLM.
It is available as extensions for Chrome, Edge and Firefox, a system-wide macOS desktop app, plugins for VS Code, Obsidian, Neovim, Zed and WordPress, and as a language server, JavaScript library and Rust crate.
Strengths
- All checks run locally with no telemetry
- Works in browsers, editors and system-wide on macOS
- Available as a language server for any LSP editor
- Supports several regional English variants
Limitations
- English only
- Rule-based checks do not rewrite text the way AI assistants do
- Desktop app is macOS only
Details
- Pricing
- FreeFree and open source.
- License
- Open source, license not stated
- Developer
- Automattic
- Platforms
- macOS, Web, Browser extension, Command line
- How it runs
- Downloadable app, Web application, Browser extension
- Works offline
- Yes
- Best suited for
- Writers and developers who want grammar checking without sending text to a server
- Categories
- Browser tools, Code editors, AI writing
- Last verified
- Added
- Sources
Alternatives to Harper
Compare allSoftware that can replace Harper for an important use case, and what changes if you switch.
Grammarly
An AI writing assistant that checks grammar and spelling and suggests rewrites and tone changes.
Grammarly adds AI rewrites, tone suggestions and an AI detector, but it requires an account, processes text on its servers and is proprietary.
Writing Tools
A system-wide desktop app that proofreads, rewrites and summarizes selected text with cloud or local LLMs.
Writing Tools is also open source and can use local LLMs to proofread and rewrite selected text on Windows, macOS and Linux, though output depends on the model.
Linguix
A grammar checker and AI rewriting assistant that works on websites through a browser extension and web editor.
Linguix checks grammar in seven languages and adds a sentence rewriter and team style guides, but it needs an account and processes text online.
Ginger
An AI writing assistant that corrects grammar, rephrases sentences and suggests synonyms in browsers and apps.
Ginger adds rephrasing, synonyms and Microsoft Office support on Windows with Android and desktop apps, but it is not open source and checks text online.
Outwrite
A grammar, style and paraphrasing assistant that works in the browser and common writing apps.
Outwrite adds paraphrasing and readability statistics in Docs, Gmail, Word and Outlook and supports French and Spanish, but it processes text in the cloud and is proprietary.
ProWritingAid
A grammar checker and style editor with planning and critique tools aimed at fiction writers.
ProWritingAid adds style and line-editing feedback with fiction planning tools across Word, a desktop editor and browser, but it is proprietary and the full feature set is paid.
QuillBot
An AI writing tool for paraphrasing, grammar checking, summarizing and generating citations.
QuillBot adds paraphrasing, summarizing and citation tools with Windows and mobile apps, but it processes text on QuillBot's servers and advanced modes need Premium.
Harper as an alternative
Listings that name Harper as an alternative.
Trinka
An AI grammar checker and writing assistant aimed at academic and technical writing.
Harper is a free, open-source checker that runs entirely on your device with no telemetry, but it is rule-based, English only and lacks academic tuning.
Writefull
AI language feedback, paraphrasing and copyediting tuned for academic writing, with Word and Overleaf plugins.
Harper is free and open source, runs locally with no telemetry and works as a language server for editors, but is rule-based and not academic-focused.
Similar software
Related functionality, not necessarily a direct replacement.
Hemingway Editor
Writing editor that highlights complex sentences and other issues to make text clearer and bolder.
Readable
An online readability checker that scores text with many readability formulas and highlights passages to fix.
Wordtune
An AI writing assistant that suggests rewrites, adjusts tone and proofreads English text.
