app-localize-behavior | Vaadin

Polymer behaviour to help internationalize your application

Published on NPM Build status Published on


app-localize-behavior is a behavior that wraps the format.js library to help you internationalize your application. Note that if you're on a browser that does not natively support the Intl object, you must load the polyfill yourself. An example polyfill can be found here.

See: Documentation, Demo.



npm install --save @polymer/app-localize-behavior

In an html file using the localized element

    <!-- Optional: Intl polyfill -->
    <script src=""></script>
    <script src=""></script>
    <script src=""></script>

    <!-- Elements using the behaviour -->
    <script type="module" src="sample-element.js"></script>

Localizing a Polymer 3 element

import {PolymerElement, html} from '@polymer/polymer';
import {mixinBehaviors} from '@polymer/polymer/lib/legacy/class.js';
import {AppLocalizeBehavior} from '@polymer/app-localize-behavior/app-localize-behavior.js';

class SampleElement extends mixinBehaviors([AppLocalizeBehavior], PolymerElement) {
  static get template() {
    return html`
      <div>{{localize('hello', 'name', 'Batman')}}</div>

  static get properties() {
    return {
      language: { value: 'en' },

  function attached() {
customElements.define('sample-element', SampleElement);


If you want to send a PR to this element, here are the instructions for running the tests and demo locally:


git clone
cd app-localize-behavior
npm install
npm install -g polymer-cli

Running the demo locally

polymer serve --npm

Running the tests

polymer test --npm


Link to this version
ImportedReleased 13 September 2018BSD 3-clause "New" or "Revised" License
Framework Support
Polymer 1.0+
Polymer 3.0+
Also supported:
Polymer 2 (2.0.2)
Browser Compatibility
Install with
npm install @polymer/app-localize-behavior"@3.0.1"
Run the above npm command in your project folder. If you have any issues installing, please contact the author.
Release notes - Version 3.0.1


  • @polymer/iron-ajax#^3.0.0-pre.26
  • @polymer/polymer#^3.0.0
  • intl-messageformat#^2.2.0