HTML resize DOM Event: Reference and Examples

When someone interacts with a webpage, the browser sends events to the relevant JavaScript code. The resize event happens when the window viewport dimensions change.

When resize happens

The window viewport dimensions change.

You can listen for it using addEventListener(). That keeps event handling separate from HTML attributes such as onclick and works well with modern code organization.

A small working example

<p>Try the relevant browser action described below.</p>
<p id="event-status" role="status">Waiting for resize...</p>
<script>
    const eventTarget = window;
    const eventStatus = document.getElementById("event-status");

    if (eventTarget) {
        eventTarget.addEventListener("resize", (eventDetails) => {
            eventStatus.textContent = "resize event received";
            console.log(eventDetails.type, eventDetails.target);
        });
    }
</script>

Reading the code

The browser listens for resize on the relevant target. When the event occurs, the callback receives eventDetails, updates the status message and logs the event name and target in Developer Tools.

Resize the browser window; use ResizeObserver for element sizes.

Watch window.innerWidth and innerHeight, not a single arbitrary element.

Some events need a specific browser condition, another tab or window, or a Web Component to reproduce. Read the trigger steps carefully before deciding that an event handler is not working.

Try it in your browser

Open the page, show the Console panel, and follow this test: Resize the browser window; use ResizeObserver for element sizes. Then change one thing in the example and observe whether the event still fires.

Common Beginner Mistakes

• Expecting resize to fire without its required user action or browser condition.
• Resize the browser window; use ResizeObserver for element sizes.
• Adding repeated event listeners without considering cleanup or unwanted side effects.

Key Takeaways

• resize reports the window viewport dimensions change.
• addEventListener("resize", ...) listens for the event on the appropriate target.
• Resize the browser window; use ResizeObserver for element sizes.