References

Beginner-friendly references for web development, with live, editable examples.

The HTML onanimationend event

Event All modern browsers Updated
Quick answer

The HTML onanimationend attribute runs JavaScript when a CSS animation completes. It is an inline handler for the animationend event; in modern code prefer addEventListener('animationend', …).

Overview

The onanimationend event attribute runs JavaScript when a CSS animation finishes. In JavaScript the event itself is named animationend — drop the on prefix when you call addEventListener.

It is a CSS animation event. The handler receives an AnimationEvent with the animationName and elapsedTime, letting you run code at specific points in a CSS animation defined with @keyframes.

You can wire this up with the inline onanimationend HTML attribute, but the modern, recommended approach is element.addEventListener('animationend', handler) in JavaScript. That keeps behavior out of your markup, lets you attach several handlers to the same event, and makes them easy to remove. The inline attribute is fine for quick demos.

Syntax

<element onanimationend="handler()">…</element>

element.addEventListener('animationend', handler);

Best practices

  • Prefer element.addEventListener('animationend', handler) over the inline onanimationend attribute — it separates behavior from markup and allows multiple handlers.
  • Use it to run JavaScript at a precise point in a CSS animation without a timer.
  • Check event.animationName when an element has more than one animation.
  • Respect prefers-reduced-motion for the animations these events track.

Frequently asked questions

What is the onanimationend event?
It runs JavaScript when a CSS animation finishes. In JavaScript the event is named animationend.
How do I run code when a CSS animation finishes?
Listen for the animationend event on the animated element.
How do I know which animation triggered the event?
Read event.animationName from the AnimationEvent.
Should I use the onanimationend attribute or addEventListener?
Prefer addEventListener('animationend', …) in JavaScript. The inline onanimationend attribute works but mixes behavior into the markup and allows only one handler per element.
onanimationcancel onanimationiteration