Grammarly → Harper

Grammarly is a capable editor, but it works by streaming everything you type to its servers — and Premium runs $12 to $30 a month for the privilege. Harper, the open-source checker backed by Automattic, takes the opposite approach: every check happens locally, in Rust and WebAssembly, returning suggestions in under ten milliseconds with no cloud round-trip, no telemetry, and no large language model quietly learning from your drafts.

For the daily work of catching typos, agreement errors, misused words, and clumsy punctuation, Harper covers the same ground you reach for Grammarly’s underline most of the time. It installs as a browser extension for Chrome and Firefox and as plugins for VS Code, Neovim, Obsidian and WordPress, so the red squiggle shows up where you already write. Because it uses a fraction of the memory — the project cites roughly one-fiftieth of LanguageTool’s footprint — it stays invisible in the background rather than bogging the page down.

What you give up is the generative layer. Harper will not rewrite a paragraph for tone, rephrase a sentence into something punchier, or draft text for you the way Grammarly’s AI features do. Its rule set is English-focused and deliberately conservative, so it flags fewer stylistic judgment calls. If your value from Grammarly came mostly from those AI rewrites, Harper is a downgrade; if it came from a reliable proofreader that never nags, it is a clear upgrade — and a private one.

Switching takes about ten minutes. Install the Harper browser extension or the plugin for your editor, confirm it is linting as you type, and uninstall the Grammarly extension. There is no account to create, nothing to import, and no data to migrate because Harper keeps no profile of you in the first place. The only adjustment is mental: you stop thinking of the grammar checker as a service and start thinking of it as a feature of your device.