Proofread the selected text with Harper — the free, open-source grammar checker that runs entirely on your Mac. Nothing is uploaded, and a check typically completes in well under a second.

Actions#

Action	What it does
Fix Writing	Applies Harper's top suggestion for every issue and returns the corrected text (paste or copy, per your OpenClip preference).
Check Writing	Shows a toast with the number of issues Harper found, e.g. `Harper found 3 issues`.
Copy Report	Copies a detailed report (line, column, category, message, suggestions) to the clipboard.
Add to Dictionary	Appends the selected word to your Harper user dictionary, so Harper and `harper-ls` stop flagging it. Only offered when a single word is selected.
Remove from Dictionary	Deletes the selected word from your Harper user dictionary again. Also limited to single-word selections.

Fix Writing understands all three of Harper's suggestion kinds — replace, insert, and remove — and applies them from the end of the selection backwards, so character offsets stay correct with multi-line text, accents, and emoji. Issues Harper reports without a suggestion are left untouched.

Requirements#

OpenClip 1.1.0 or later.
Harper — install the CLI with brew install harper (or cargo install --locked --git https://github.com/Automattic/harper.git harper-cli). The extension looks for harper-cli in /opt/homebrew/bin, /usr/local/bin, ~/.cargo/bin, and on PATH.
jq — bundled with macOS 15 and later, otherwise brew install jq.

If either binary is missing, the action shows a toast telling you what to install instead of failing silently.

Options#

English dialect (dialect) — american (default), british, canadian, or australian. Passed to Harper as --dialect, so British spellings such as colour are not flagged when you pick british.

Privacy#

The selection is piped to the local harper-cli process on stdin and never leaves your machine. Harper does no telemetry and needs no network access.

Usage#

Select some prose anywhere on your Mac.
Open the OpenClip popup and choose Harper.
Pick Fix Writing to rewrite the selection, or Check Writing / Copy Report to review the issues first.

Notes#

The user dictionary lives at ~/Library/Application Support/harper-ls/dictionary.txt, the same file harper-ls uses in your editor.
OpenClip decides which actions to show from the selection alone, so Remove from Dictionary is offered for any single word rather than only for words already in the dictionary. Picking it for a word that is not there just reports that, and changes nothing.
OpenClip stores option values per action, so the dialect is read from the action you configured and reused by the other Harper actions.

Credits#

The icon is Harper's own logo, taken from packages/obsidian-plugin/logo.svg in the Automattic/harper repository (Apache-2.0), recentred into a square viewBox and left monochrome so it inherits the OpenClip theme colour.

Harper