One important thing to consider about this config is that you can whitelist specific modules to not treat as webpack `externals`. There aren't many use cases where this functionality is need, but for the case of Vue UI libraries that provide raw `*.vue` components they will need to be whitelisted, so `vue-loader` is able to compile them. Another use case would be using webpack `alias`es, such as setting `vue` to import the full Compiler + Runtime build. Because of this, `vue` is already in the whitelist.