The Page Visibility API is a browser feature that allows developers to detect and respond to changes in the visibility state of a web page. This API can optimize performance and user experience by adjusting tasks based on whether a page is visible to the user or hidden in the background.

What is the Page Visibility API?

The Page Visibility API provides information about the visibility state of a webpage. For instance, when a user switches tabs, minimizes their browser, or locks their screen, the API detects these changes and enables developers to adjust the page’s behavior accordingly.

Key Benefits:

1. Performance Optimization: Pause animations, videos, or other resource-intensive processes when the page is not visible.
2. Battery Efficiency: Reduce unnecessary activity to save battery life on mobile devices.
3. Better Analytics: Track active user engagement with more precision.

How the Page Visibility API Works

The API is built around the document.visibilityState property and the visibilitychange event.

Visibility States:

• visible: The page is in the foreground and visible to the user.
• hidden: The page is not visible, either because the user switched tabs or minimized the browser.

Key Properties:

1. document.visibilityState Returns the current visibility state of the page (visible or hidden).
2. document.hidden A boolean property that returns true if the page is hidden.
3. visibilitychange Event An event that fires whenever the visibility state of the page changes.

How to Use the Page Visibility API

Basic Example:

Detect when a page becomes hidden or visible:

document.addEventListener(‘visibilitychange’, () => {

    if (document.visibilityState === ‘hidden’) {

        console.log(‘Page is hidden’);

        // Pause tasks like video playback or data fetching

    } else if (document.visibilityState === ‘visible’) {

        console.log(‘Page is visible’);

        // Resume tasks or animations

    }

});

Applications of the Page Visibility API

1. Optimizing Resource Usage

Reduce the load on system resources by pausing:

• Video or audio playback.
• Intensive calculations or animations.
• Data polling or network requests.

2. Improving User Experience

Maintain a smooth experience by resuming tasks only when the user returns to the page.

Example: Pausing Video Playback

document.addEventListener(‘visibilitychange’, () => {

    const video = document.querySelector(‘video’);

    if (document.visibilityState === ‘hidden’ && !video.paused) {

        video.pause();

    } else if (document.visibilityState === ‘visible’ && video.paused) {

        video.play();

    }

});

3. Enhanced Analytics

Track real user engagement by distinguishing between active and passive users:

• Record time spent actively viewing the page.
• Filter out background tab activity from engagement metrics.

Compatibility and Browser Support

The Page Visibility API is supported by all modern browsers, including:

• Google Chrome
• Mozilla Firefox
• Microsoft Edge
• Safari

Developers should always test their implementations across browsers for consistent behavior.

Best Practices

1. Fallback Support
   Older browsers may not support the API, so ensure graceful degradation for critical features.
2. Use Visibility Change Wisely
   Don’t overload the visibilitychange event listener with heavy computations, as this can negate performance benefits.

Combine with Other APIs
Integrate the Page Visibility API with APIs like Battery Status API or Network Information API for better resource management.