zilvestro/grammai

AI writing assistance. Free & open source.

Offline English and German grammar checks, with rewrites and translation through your own Claude Code or Codex account.

Sponsored by Affonso

Get started · Connect your AI · Contribute · GPL 3.0

grammai is 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.

The extension is free. English and German spelling and grammar work on your device, without an account or extra software. Optional AI features use your own signed-in Claude Code or Codex CLI. Your provider's access requirements and usage limits apply; grammai does not include an AI subscription.

• Spelling and grammar, offline. English and German engines and dictionaries are bundled with the extension.
• Context matters. Local grammar rules and targeted word-confusion checks cover constructions such as “Ist das wirklich war?” → “Ist das wirklich wahr?” An optional AI context check handles a broader passage.
• Corrections in place. Hover to highlight a marked word, click to review, then accept or dismiss. Undo restores the last grammai edit.
• Rewrites in your voice. Improve clarity, shorten a passage, change the tone, or save your own named prompts.
• Translate and keep writing. Translate between English and German and replace the selection, or the active field, in one action.
• Quiet by default. The action pill appears only when you select text. Light and dark modes, keyboard shortcuts and per-site controls are included.

Automatic German checking	Rewrites with your own AI

English ↔ German translation	Your prompts, in dark mode

Screenshots use sample drafts in a separate browser profile. The rewrite shown was generated through the installed AI CLI. They contain no personal browsing session or account data.

Chrome Web Store — coming soon. The button above is a placeholder until the first listing is available. Store users will install the extension once; ordinary grammar checks need no additional setup.

To try the current source build:

npm ci
npm run build

Use Node.js 22 or newer to build the project. Open chrome://extensions, enable Developer mode, choose Load unpacked, and select the generated dist directory. Helium uses the same extension management screen.

Open a supported text field and start writing. German and English are detected automatically. Grammar checking needs no helper, Java, Homebrew, LanguageTool installation, API key or sign-in. The German engine takes a few seconds to initialize on its first check.

Language preferences and the English spelling variant are available under All settings. After rebuilding an unpacked extension, reload it and the website tabs where you want to use the new version.

Rewrites, translation and AI context checks currently use the official Claude Code or Codex CLI through a one-time local helper installation. The helper installer currently supports macOS. Open All settings → Help & setup → Your AI for the guide and connection check, or read AI setup.

The helper is required for this local CLI connection. A detected CLI is not proof of sign-in or model access; a successful rewrite verifies those. There is no grammai-hosted AI service in this release.

Browser shortcuts can be changed at chrome://extensions/shortcuts. Operating system or browser shortcuts may take precedence.

Ordinary checks stay inside your browser. grammai includes no analytics, telemetry or automatic crash uploads. Preferences, personal words, saved prompts and paused website hostnames are stored in local extension storage.

An explicit AI action sends the selected text—or the active field without a selection—to your chosen provider through its CLI. Provider terms and account settings apply. Feedback opens an email draft that you send yourself; writing and page URLs are not attached automatically.

Read the privacy policy or data-flow explanation.

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 and German. This release does not claim full Grammarly or LanguageTool parity.

We want to build grammai with the community. Found a bug? Have an idea for a better editor integration, a grammar fix or a new feature? Open an issue or send a pull request—small improvements are welcome.

Fork this repository, create a branch for your change, and open a pull request against main. Explain what changes for users and how you checked it. For larger features, start with an issue so we can agree on scope before you invest time.

Contributing covers the project layout, tests and how to report editor issues. Development describes the local engines and native helper. Release preparation covers Store packaging and publication assets.

Report a problem through Send feedback in the assistant or email grammai@zaapp.io. Include the website/editor, browser and a short, anonymized example. Keep private drafts and account credentials out of reports.

The original grammai code is licensed under GNU GPL version 3 (GPL-3.0-only). Bundled engines, dictionaries and other dependencies retain their respective upstream licenses. See third-party notices.

grammai is an independent project and is not affiliated with Grammarly, LanguageTool, Anthropic or OpenAI.