You can totally use ES6 modules, you just have to split the web component JavaScript and HTML into separate files. That&#x27;s what we did for Home Assistant, which we documented here: <a href="https:&#x2F;&#x2F;github.com&#x2F;home-assistant&#x2F;home-assistant-polymer#building-the-app" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;home-assistant&#x2F;home-assistant-polymer#bui...</a>