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, Web-based and Self-Hosted apps. The best Polymer alternative is Vue.js, which is both free and Open Source. Other great apps like Polymer are Angular, React, Svelte and Vite.