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

Target	Use when	Example
`chromium`	Fast default local development	`extension dev --browser=chromium`
`chrome`	Validating Chrome-specific behavior	`extension dev --browser=chrome`
`edge`	Validating Edge distribution behavior	`extension dev --browser=edge`
`firefox`	Validating Gecko compatibility and APIs	`extension dev --browser=firefox`
`chrome,firefox`	Release checks across both major engines	`extension build --browser=chrome,firefox`
`chromium-based`	Running custom Chromium binaries (Brave, Arc, etc.)	`extension dev --browser=chromium-based --chromium-binary=/path/to/browser`
`gecko-based`	Running custom Firefox-family binaries	`extension dev --browser=gecko-based --gecko-binary=/path/to/browser`

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

If no browser is provided, CLI defaults to chromium.

Video demo soon: named browser targets

Named browser targets:

Browser	Usage
Chrome	`npx extension dev --browser=chrome`
Edge	`npx extension dev --browser=edge`
Firefox	`npx extension dev --browser=firefox`
Chromium	`npx extension dev --browser=chromium`

Engine-based targets (custom binary required):

Engine target	Usage
Chromium-based	`npx extension dev --browser=chromium-based --chromium-binary=/path/to/browser`
Gecko-based (`firefox-based`)	`npx extension dev --browser=gecko-based --gecko-binary=/path/to/browser`

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

Video demo soon: engine-based target binaries

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).

Video demo soon: multi-browser selection flow

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.

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.

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