HTML online DOM Event: Reference and Examples

When someone interacts with a webpage, the browser sends events to the relevant JavaScript code. The online event happens when the browser reports restored network connectivity.

When online happens

The browser reports restored network connectivity.

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 online...</p>
<script>
    const eventTarget = window;
    const eventStatus = document.getElementById("event-status");

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

Reading the code

The browser listens for online 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.

Return from offline mode; online does not guarantee the server is reachable.

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: Return from offline mode; online does not guarantee the server is reachable. Then change one thing in the example and observe whether the event still fires.

Common Beginner Mistakes

• Expecting online to fire without its required user action or browser condition.
• Return from offline mode; online does not guarantee the server is reachable.
• Adding repeated event listeners without considering cleanup or unwanted side effects.

Key Takeaways

• online reports the browser reports restored network connectivity.
• addEventListener("online", ...) listens for the event on the appropriate target.
• Return from offline mode; online does not guarantee the server is reachable.