#Multi-platform builds

Build and package the same extension for multiple browsers with predictable outputs.

Ship the same extension to Chrome, Edge, and Firefox without maintaining separate build scripts. Extension.js can run production builds per target, write artifacts to dist/<browser>, and optionally generate zip packages for distribution.

#How it works

Run a production build:

npx extension build

pnpx extension build

yarn dlx extension build

Default browser target is chromium unless overridden.

#Browser selection

You can target a specific browser/engine:

npx extension build --browser=chrome

pnpx extension build --browser=chrome

yarn dlx extension build --browser=chrome

npx extension build --browser=firefox

pnpx extension build --browser=firefox

yarn dlx extension build --browser=firefox

Supported values include:

• chrome
• edge
• firefox
• chromium
• chromium-based
• gecko-based / firefox-based (aliases)

You can also run a build matrix in one command:

npx extension build --browser=chrome,edge,firefox

pnpx extension build --browser=chrome,edge,firefox

yarn dlx extension build --browser=chrome,edge,firefox

This builds sequentially for chrome, edge, and firefox.

#Output layout

Each target writes to its own folder:

• dist/chrome
• dist/edge
• dist/firefox
• dist/chromium
• dist/chromium-based
• dist/gecko-based

#Build capabilities

#Generating a zip file

Generate a distribution zip from each target output with --zip:

npx extension build --zip

pnpx extension build --zip

yarn dlx extension build --zip

By default, the zip name uses sanitized manifest name + version, for example:

• my-extension-1.0.0.zip

Customize filename:

npx extension build --zip --zip-filename=my-release

pnpx extension build --zip --zip-filename=my-release

yarn dlx extension build --zip --zip-filename=my-release

This creates my-release.zip inside the target dist/<browser> folder.

#Include source archive

Use --zip-source to generate a source archive alongside distribution output.

--zip-source produces:

• dist/<name>-<version>-source.zip

#Polyfill support

If your code relies on Gecko-style browser.* APIs and you need Chromium compatibility, enable --polyfill:

npx extension build --polyfill

pnpx extension build --polyfill

yarn dlx extension build --polyfill

#Best practices

• Build per target in CI: Treat each browser output as an independent artifact.
• Use a browser matrix command for parity checks: Catch target-specific issues early in one pipeline step.
• Package intentionally: Use --zip for store uploads and --zip-source for traceable source artifacts.
• Keep target config explicit: Use extension.config.* command/browser defaults for reproducible builds.

#Next steps

• Learn more about the Browsers Available.
• Explore Path Resolution for asset/output mapping details.