Polymer was an open-source JS library for web components Launched May 29, 2015; shut down April 20, 2021 — it lived 5 years. One of 32 Google products killed in 2021. Polymer is a discontinued open-source JavaScript library for building web applications using Web Components. The library is being developed by Google developers and contributors on GitHub. Modern design principles are implemented as a separate project using Google's Material Design design principles. http://polymer-project.org Data: Killed by Google (killedbygoogle.com, MIT).