paper-checkbox is a button that can be either checked or unchecked. User can
tap the checkbox to check or uncheck it. Usually you use checkboxes to allow
user to select multiple options from a set. If you have a single ON/OFF option,
avoid using a single checkbox and use paper-toggle-button instead.
See: Documentation, Demo.
npm install --save @polymer/paper-checkbox
<html>
  <head>
    <script type="module">
      import '@polymer/paper-checkbox/paper-checkbox.js';
    </script>
  </head>
  <body>
    <paper-checkbox>Unchecked</paper-checkbox>
    <paper-checkbox checked>Checked</paper-checkbox>
    <paper-checkbox disabled>Disabled</paper-checkbox>
  </body>
</html>import {PolymerElement} from '@polymer/polymer/polymer-element.js';
import {html} from '@polymer/polymer/lib/utils/html-tag.js';
import '@polymer/paper-checkbox/paper-checkbox.js';
class ExampleElement extends PolymerElement {
  static get template() {
    return html`
      <paper-checkbox>Unchecked</paper-checkbox>
      <paper-checkbox checked>Checked</paper-checkbox>
      <paper-checkbox disabled>Disabled</paper-checkbox>
    `;
  }
}
customElements.define('example-element', ExampleElement);If you want to send a PR to this element, here are the instructions for running the tests and demo locally:
git clone https://github.com/PolymerElements/paper-checkbox
cd paper-checkbox
npm install
npm install -g polymer-clipolymer serve --npm
open http://127.0.0.1:<port>/demo/polymer test --npm