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Videos and animations can make your website engaging and dynamic. However, they are also common culprits for slow page loads and poor performance.

Optimizing how you deliver and use media is crucial for a fast and smooth user experience.

Large video files and inefficient animations can significantly impact your website's speed. This leads to:

• Slow Load Times: Users might leave before content appears.
• High Bandwidth Usage: Costly for both users and servers.
• Janky User Experience: Animations that stutter or lag feel unprofessional.

Optimizing them improves user satisfaction and reduces bounce rates.

Choosing the right video format and codec is the first step. Modern codecs offer better compression without sacrificing much quality.

• WebM (VP9/AV1): Excellent compression, ideal for web.
• MP4 (H.264): Widely supported, good balance.
• AV1: Next-gen codec offering superior compression, gaining support.

Always provide multiple <source> tags for browser compatibility.

The preload attribute tells the browser how much video data to fetch initially. metadata is often a good balance, fetching just enough to show dimensions and duration.

The poster attribute allows you to display an image before the video loads or while it's loading, improving perceived performance and user experience.

Ensure your videos adapt well to different screen sizes. A common technique for maintaining aspect ratio for embedded videos (like YouTube/Vimeo iframes) uses CSS padding tricks.

This wraps the video in a container that scales proportionally.

Most modern browsers have strict autoplay policies to prevent annoying users and conserve data. Videos often need to be muted or user-initiated to autoplay.

Using playsinline allows the video to play within the element's playback area on iOS, rather than automatically entering fullscreen.

When animating with CSS, prefer properties that browsers can handle efficiently. transform and opacity are often GPU-accelerated, meaning they don't force layout recalculations.

Animating properties like width, height, top, or left can trigger expensive layout and paint operations, leading to jank.

The CSS will-change property is a hint to the browser that an element is expected to change in the near future. This allows the browser to perform optimizations beforehand.

Use it sparingly and only on elements that are actually animating, as it can consume resources if overused.

To ensure smooth and performant animations:

• Keep it Short: Aim for durations under 500ms.
• Use `cubic-bezier`: For natural-looking easing.
• Avoid `auto`: Don't animate `height: auto` or `width: auto`.
• Test on Low-End Devices: What looks smooth on a desktop might not on a mobile device.

Review what you've learned about optimizing videos and animations. Select all the correct statements.

You've learned how to optimize video and animation performance!

• Choose efficient video formats and codecs.
• Use preload and poster attributes for better video delivery.
• Implement responsive video techniques.
• Respect browser autoplay policies.
• Prioritize GPU-accelerated CSS properties like transform and opacity for animations.
• Use will-change judiciously for performance hints.

Next, you'll dive into JavaScript performance best practices!