Fusion supports a .fusionrc.js in the root directory of your application. This must be a CommonJS module exporting an object.

This configuration object supports the following fields:


Adding plugins/presets

For example, to add your own Babel plugins/preset:

module.exports = {
  babel: {
    presets: ["some-babel-preset"],
    plugins: ["some-babel-plugin"]

Please note that custom Babel config is an unstable API and may not be supported in future releases.


By default this is false.

Setting this to true enables the assumption that modules in your code do not have any import side effects. This assumption allows for more powerful tree shaking and pruning of unused imports.

This option may be useful if you import modules that use Node.js built-ins. This option makes it easier to avoid unintentionally including server-specific code in the browser bundle.

For specifics regarding implementation details, see:

In the future, it is possible that some form of this behavior may be turned on by default (with ways to opt-out instead).


This is an optional property that can be used to override the Fusion.js defaults for https://webpack.js.org/configuration/node/ in the browser bundle.

module.exports = {
  nodeBuiltins: {
    Buffer: true