grammai

What does grammai do?

The README describes grammai as "an open-source writing assistant for Chrome and Chromium browsers such as Helium. It checks what you write, highlights issues in place, and lets you apply corrections without leaving the editor." Spelling and grammar for English, German and Romanian run inside the browser, with the engines and dictionaries bundled in the extension.

Optional features use a model you connect: AI rewrites in your voice (clarity, shorten, change tone, or save your own named prompts), translation between English and German or Romanian with replace-selection or replace-active-field, and an AI context check that handles a broader passage. These features currently use the official Claude Code or Codex CLI through a one-time local helper that supports macOS.

Key facts

• Licence: GNU GPL version 3 (GPL-3.0-only), on the original grammai code. Bundled engines, dictionaries and other dependencies keep their upstream licences; see THIRD_PARTY_NOTICES.md.
• Languages for offline grammar: English, German and Romanian, with grammar rules and targeted word-confusion checks.
• Platform: Chrome and Chromium (including Helium) on macOS, Windows and Linux. The AI helper for the local CLI connection currently supports macOS.
• AI providers for rewrites, translation and context: the Claude Code or Codex CLI the user is signed in to, through a local helper. There is no grammai-hosted AI service.
• Shortcuts: ⌘⇧Y or Ctrl Shift Y to open the assistant; ⌘⇧K for rewrite; ⌘⇧L for translation; Alt↓ and Alt↑ for next and previous correction; Alt Enter to accept; Alt Backspace to dismiss; Alt Z to undo the last grammai edit.
• Build: npm ci && npm run build with Node.js 22 or newer. Load unpacked from dist/ in chrome://extensions.
• Beta scope: textareas, suitable text inputs, standard contenteditable fields and tested Draft.js flows including X-style editors. Google Docs canvas and general Shadow DOM, Slate and ProseMirror adapters are not complete.
• Privacy: no analytics, telemetry or automatic crash uploads. Preferences, personal words, saved prompts and paused website hostnames are stored in local extension storage.

What does it replace, and where does it fall short?

grammai replaces Grammarly for a reader of English, German or Romanian who wants grammar and spelling checks that stay on the device, with AI rewrites optional and run through a CLI they already pay for. It appears on the open-source alternatives to Grammarly page.

Where it falls short: the AI helper is currently macOS only, so Windows and Linux users get offline grammar and spelling without AI rewrites. The README says "this release does not claim full Grammarly or LanguageTool parity." Grammar coverage is limited, context suggestions can be wrong, and Google Docs canvas and general Shadow DOM, Slate and ProseMirror adapters are not complete. The German and Romanian engines take a few seconds to initialise on their first check.

How does grammai run?

Install from the Chrome Web Store, or build from source with Node.js 22 or newer: npm ci && npm run build, then open chrome://extensions, enable Developer mode, choose Load unpacked and pick dist/. Helium uses the same extension management screen.

Ordinary grammar checks need no helper, no Java, no Homebrew, no LanguageTool install, no API key and no sign-in. For AI rewrites, translation and context, open All settings and the Help & setup page: the connection check installs a one-time local helper (macOS) that talks to the official Claude Code or Codex CLI. A detected CLI is not proof of sign-in or model access; a successful rewrite verifies those.

Who is grammai for?

A reader of English, German or Romanian who wants browser grammar and spelling checks on the device, under GPL-3.0, and who wants AI rewrites and translation to run through a CLI they already use. For writing lint on markdown and prose from the command line, see Vale. For LaTeX and Markdown offline grammar, see LTeX+. For a hosted all-in-one product, Grammarly is the paid tool.

What limits does the README state?

• "Beta scope: current support covers textareas, suitable text inputs, standard contenteditable fields and tested Draft.js editing flows, including X-style editors. Dedicated Google Docs canvas support and general Shadow DOM, Slate and ProseMirror adapters are not complete."
• "Language detection can be ambiguous on short or mixed-language text. Grammar coverage is limited, and context suggestions can be wrong. AI translation currently supports English, German and Romanian."
• "This release does not claim full Grammarly or LanguageTool parity."
• "The helper installer currently supports macOS."

Questions people ask

Is grammai open source?

Yes. The LICENSE file at the repository root is GNU GPL version 3 (GPL-3.0-only), an OSI-approved licence. The README says the original grammai code is licensed under GNU GPL version 3; bundled engines, dictionaries and other dependencies keep their own licences, listed in THIRD_PARTY_NOTICES.md.

Does grammai work without the internet?

Yes, for the grammar and spelling checks. English, German and Romanian engines and dictionaries are bundled with the extension and run in the browser. AI rewrites, translation and context checks need the local helper and your Claude Code or Codex CLI; those features send the selected text, or the active field, to the provider through the CLI.

How does grammai use my Claude Code or Codex account?

A one-time local helper (macOS) is installed through the extension's settings. The helper talks to the official Claude Code or Codex CLI you are signed in to. There is no grammai-hosted AI service. A detected CLI is not proof of sign-in or model access; the first successful rewrite verifies those. Your provider's access requirements and usage limits apply.

How does grammai compare with Grammarly?

Grammarly is a hosted product. grammai is a Chrome and Chromium extension that keeps grammar checks on the device, with AI features gated behind your own CLI sign-in, under GPL-3.0. The README says the current beta does not claim full Grammarly or LanguageTool parity. The open-source alternatives to Grammarly page sets grammai beside Harper, LanguageTool, Writing Tools, Vale and LTeX+.

Where are my preferences stored?

In the extension's local storage, in the browser. The README says preferences, personal words, saved prompts and paused website hostnames stay in the browser. There are no analytics, no telemetry and no automatic crash uploads. Feedback is sent only when you submit the form; the message, any screenshots you attach and the extension version are included.

Sources

• grammai README and LICENSE: github.com/zilvestro/grammai, read 2026-11-02.