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Polymer App Toolbox - Starter Kit

Build Status

This template is a starting point for building apps using a drawer-based layout. The layout is provided by app-layout elements.

This template, along with the polymer-cli toolchain, also demonstrates use of the "PRPL pattern" This pattern allows fast first delivery and interaction with the content at the initial route requested by the user, along with fast subsequent navigation by pre-caching the remaining components required by the app and progressively loading them on-demand as the user navigates through the app.

The PRPL pattern, in a nutshell:

  • Push components required for the initial route
  • Render initial route ASAP
  • Pre-cache components for remaining routes
  • Lazy-load and progressively upgrade next routes on-demand



Install Polymer CLI using npm (we assume you have pre-installed node.js).

npm install -g polymer-cli
Initialize project from template
mkdir my-app
cd my-app
polymer init polymer-3-starter-kit

Start the development server

This command serves the app at and provides basic URL routing for the app:

npm start


The npm run build command builds your Polymer application for production, using build configuration options provided by the command line or in your project's polymer.json file.

You can configure your polymer.json file to create multiple builds. This is necessary if you will be serving different builds optimized for different browsers. You can define your own named builds, or use presets. See the documentation on building your project for production for more information.

The Polymer Starter Kit is configured to create three builds. These builds will be output to a subdirectory under the build/ directory as follows:

  • es5-bundled is a bundled, minified build with a service worker. ES6 code is compiled to ES5 for compatibility with older browsers.
  • es6-bundled is a bundled, minified build with a service worker. ES6 code is served as-is. This build is for browsers that can handle ES6 code - see building your project for production for a list.
  • esm-bundled is a bundled, minified build with a service worker. It uses standard ES module import/export statements for browsers that support them.

Run polymer help build for the full list of available options and optimizations. Also, see the documentation on the polymer.json specification and building your Polymer application for production.

Preview the build

This command serves your app. Replace build-folder-name with the folder name of the build you want to serve.

npm start build/build-folder-name/

Run tests

This command will run Web Component Tester against the browsers currently installed on your machine:

npm test

If running Windows you will need to set the following environment variables:


Read More here daffl/launchpad

Looking for our older PSK2 Polycast or migration blog post? See the previous README.