Polymer is described as 'library that uses the latest web technologies to let you create custom HTML elements. Build anything from a button to a complete application as an encapsulated, reusable element that works across desktop and mobile' and is an app in the Development category. There are more than 50 alternatives to Polymer for a variety of platforms, including Windows, Linux, Mac, Online / Web-based and Self-Hosted solutions. The best alternative is Vue.js, which is both free and Open Source. Other great apps like Polymer are React (Free, Open Source), AngularJS (Free, Open Source), Materialize (Free, Open Source) and Svelte (Free, Open Source).