ext0.dev

Open-source, all-in-one developer-tools browser extension for Chrome. Inspect CSS, pick colors, measure pages, preview responsive layouts, format JSON, and export elements from one toolbar.

Status

ext0 is currently a public beta. It is not available on the Chrome Web Store yet, but you can build it from source and load it locally as an unpacked Chrome extension.

Features

• CSS Inspector - inspect typography, layout, spacing, colors, and styles directly on the page.
• Color Picker - pick page colors and copy them in common formats.
• Page Ruler - measure distances and element sizes in the browser.
• Responsive Viewer - preview a page across common device sizes.
• JSON Formatter - auto-render JSON pages in a readable view.
• Export Element - copy selected HTML/CSS or open it in CodePen.
• Content Lab - save posts and pages as local clips (text excerpt, media, engagement stats) and export them as a ZIP.

Install Locally

Requirements:

• Node.js 22+
• pnpm 9+

Build and load the Chrome extension:

pnpm install
pnpm --filter @ext0/extension build

Then open chrome://extensions, enable Developer mode, choose Load unpacked, and select:

apps/extension/.output/chrome-mv3

After pulling updates, run the build command again and reload the extension from chrome://extensions.

Privacy

ext0 has no accounts, payments, telemetry, or background reporting. Extension settings and Content Lab clips are stored locally in your browser and never sent anywhere. The only outbound requests are user-triggered: the Export Element tool can post selected HTML/CSS to CodePen when you click Open in CodePen, and exporting Content Lab clips as a ZIP downloads the clipped media images from the site that hosts them so they can be included in the archive.

Read the full privacy policy, the extension permission notes, or the security policy.

Limitations

• ext0 is not yet published on the Chrome Web Store.
• Chrome blocks extensions on internal pages such as chrome:// URLs and the Chrome Web Store.
• Local installs are manual; rebuild and reload after updating the source.

Development

This monorepo contains two packages:

Package	Path	Description
@ext0/extension	apps/extension	Browser extension built with WXT, React, and Tailwind.
@ext0/web	apps/web	Marketing site at ext0.dev, built with Astro, React islands, and Tailwind.

Run the full workspace:

pnpm dev

Run a specific app:

pnpm --filter @ext0/extension dev
pnpm --filter @ext0/web dev

Common checks:

pnpm lint
pnpm typecheck
pnpm build

Contributing

Issues, ideas, and pull requests are welcome. Start with CONTRIBUTING.md, and please follow the Code of Conduct.

For help, visit support, open a GitHub issue, or start a GitHub discussion.

License

MIT (c) Wahyu Syahputra.