[](https://travis-ci.org/PolymerElements/iron-validatable-behavior) _[Demo and API docs](https://elements.polymer-project.org/elements/iron-validatable-behavior)_ ##Polymer.IronValidatableBehavior `Use Polymer.IronValidatableBehavior` to implement an element that validates user input. Use the related `Polymer.IronValidatorBehavior` to add custom validation logic to an iron-input. By default, an `` element validates its fields when the user presses the submit button. To validate a form imperatively, call the form's `validate()` method, which in turn will call `validate()` on all its children. By using `Polymer.IronValidatableBehavior`, your custom element will get a public `validate()`, which will return the validity of the element, and a corresponding `invalid` attribute, which can be used for styling. To implement the custom validation logic of your element, you must override the protected `_getValidity()` method of this behaviour, rather than `validate()`. See [this](https://github.com/PolymerElements/iron-form/blob/master/demo/simple-element.html) for an example. ### Accessibility Changing the `invalid` property, either manually or by calling `validate()` will update the `aria-invalid` attribute.