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_[Demo and API docs](https://elements.polymer-project.org/elements/iron-collapse)_


##<iron-collapse>

`iron-collapse` creates a collapsible block of content.  By default, the content
will be collapsed.  Use `opened` or `toggle()` to show/hide the content.

```html
toggle collapse


  
Content goes here...


...

toggle: function() {
  this.$.collapse.toggle();
}
```

`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.

```html



  

    
Content goes here...
  

```

### Styling

The following custom properties and mixins are available for styling:

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