Builder-Webpack4

Builder implemented with webpack4 and webpack4-compatible loaders/plugins/config, used by @storybook/core-server to build the preview iframe.

builder-webpack4 is the default, so no configuration is necessary to use it. However, if you wan to explicitly configure your Storybook to run builder-webpack4, install it as a dev dependency and then update your .storybook/main.js configuration.

module.exports = {
  core: {
    builder: 'webpack4',
  },
};