# Choosing which browsers PageBuilder Engine to support

Source: https://dev.arcxp.com/pagebuilder-engine/how-to-guides/optimization-and-deployment/choosing-which-browsers-pagebuilder-engine-to-support/

PageBuilder Engine 4.0 brings support for [Browserslist](https://browsersl.ist/). Developers can configure their bundles to specify which browsers and versions to support so that Engine can include and remove the appropriate JS (for example, polyfills) and CSS.

## Enabling Browserslist support

To enable Browserslist, you must specify a new field in your bundle’s `package.json`.

For example:

```json
...

  "browserslist": [
    "defaults and supports es6-module",
    "maintained node versions"
  ]

...
```

By default, Fusion provides `defaults and not ie 11`. To review the default configuration of the browserlist that Engine supports, see [Browserslist](https://browsersl.ist/#q=defaults).

After you add your desired browserslist configuration, run `npx browserslist` to validate it and receive a list of supported browsers.

## Verifying the generated output

To analyze the generated JS and CSS, run:

```
npx webpack-bundle-analyzer .fusion/dist/stats.json .fusion/dist/components/combinations/
```

## Considerations

At this time, PageBuilder Engine supports only a provided configuration in your bundle’s `package.json` file. The `.browserslistrc` files are not supported at this time.