#Browsers available

Run and test your extension across major browsers from one CLI workflow.

Validate one extension across Chrome, Edge, Firefox, and custom browser binaries from one command surface.

#Choose the right target

#How it works

Use --browser to select a target in dev, start, preview, and build.

If no browser is provided, CLI defaults to chromium.

#Supported browsers

Named browser targets:

Engine-based targets (custom binary required):

firefox-based is treated as a Gecko engine target internally.

#Multi-browser selection

You can run multiple named browsers in one command:

npx extension dev --browser=chrome,firefox

Use comma-separated values to run multiple named targets in sequence (for example --browser=chrome,edge,firefox).

#Constraints and behavior

• chromium-based requires --chromium-binary.
• gecko-based / firefox-based require --gecko-binary.
• Engine-based targets route to the same Chromium/Firefox runners with engine-aware behavior.

#Best practices

• Use named browsers for daily iteration: chrome, edge, and firefox are the fastest path for regular testing.
• Use engine-based mode intentionally: Prefer chromium-based / gecko-based only when validating custom binaries.
• Keep profiles isolated per browser: Reduce cross-browser state leakage while debugging.
• Pair with browser-specific fields: Use browser-prefixed manifest keys for true behavior differences.

#Next steps

• Customize browser flags.
• Customize browser preferences.
• Run other browsers from custom binaries.