Open source alternatives to Grammarly

One project on starwire does the same job. Ranked by how much of what Grammarly does each one covers, read from its README and website. Ties go to the most active.

What Grammarly does

Grammar and spelling checkscore
Works in apps and the browser as you typecore
Clarity and style suggestions
Tone detection
AI rewriting
Plagiarism check

Each dot in the table is one job, in this order. Square dots are core jobs and count double. Full means yes, half means partly. "See the evidence" under a project shows the line behind each one. Coverage is what a project documents, not how well it works or how hard it is to move to. How we score this

Project	Covers	Stars	Commits, 12 weeks	Last release	Closed vs opened	Setup	License
harperOffline grammar checker written in Rust with a WebAssembly build	Covers one part56%	18k+234	406	yesterday	27%	Install like an app	Apache-2.0
Covers all 2 core jobs. Partly: Clarity and style suggestions. Not shown: Tone detection; AI rewriting; Plagiarism check.See the evidence Grammar and spelling checkscoreYesimproper capitalization, misspelled words, awkward phrasing Works in apps and the browser as you typecoreYesmacOS, every text field, system-wide. Clarity and style suggestionsPartlyawkward phrasing Tone detectionNot shownNeither the README nor the website mentions it. AI rewritingNot shownNeither the README nor the website mentions it. Plagiarism checkNot shownNeither the README nor the website mentions it.

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