Polymer is an open source JavaScript library maintained by Google for building web applications using web components. It also supports both one-way and two-way data binding, creating a broader scope. When you compare Angular to Polymer, since both are built by Google, Angular is a comprehensive framework for developing web applications, whereas Polymer is just a library for developing web components. It was the first library to allow you to create interactive applications using web components. There are currently over 3000 websites using Polymer such as virustotal.com, rogers.com, zeplin.io and so on.