iron-collapse | Vaadin

Adds collapsible behavior to a target element

Published on NPM Build status Published on


iron-collapse creates a collapsible block of content. By default, the content will be collapsed. Use opened or toggle() to show/hide the content. The aria-expanded attribute should only be set on the button that controls the collapsable area, not on the area itself. See

iron-collapse adjusts the max-height/max-width of the collapsible element to show/hide the content. So avoid putting padding/margin/border on the collapsible directly, and instead put a div inside and style that.

  .collapse-content {
    padding: 15px;
    border: 1px solid #dedede;

  <div class="collapse-content">
    <div>Content goes here...</div>


The following custom properties and mixins are available for styling:

Custom property Description Default
--iron-collapse-transition-duration Animation transition duration 300ms

See: Documentation, Demo.



npm install --save @polymer/iron-collapse

In an html file

    <script type="module">
      import '@polymer/iron-collapse/iron-collapse.js';
    <iron-collapse id="collapse">
      <div>Content goes here...</div>

In a Polymer 3 element

import {PolymerElement, html} from '@polymer/polymer';
import '@polymer/iron-collapse/iron-collapse.js';

class SampleElement extends PolymerElement {
  static get template() {
    return html`
      <iron-collapse id="collapse">
        <div>Content goes here...</div>
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 iron-collapse
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 14 September 2018BSD 3-clause "New" or "Revised" License
Framework Support
Polymer 1.0+
Polymer 3.0+
Also supported:
Polymer 2 (2.2.1)
Browser Compatibility
Install with
npm install @polymer/iron-collapse"@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-resizable-behavior#^3.0.0-pre.26
  • @polymer/polymer#^3.0.0