Within WordPress 5.4, one of the latest features is called Lazy Loading. Lazy Loading means to wait until the user’s browser viewport is within a certain distance before downloading image/videos creating a faster website experience.

This is how Lazy Loading works:

The browser builds the web page Document Object Model without downloading images and preloading videos.

JavaScript is then used to determine which images to download and which videos to preload based on the content that is initially visible when the page loads. Those images and videos are downloaded and preloaded based on location on the page.

Downloading and rendering of additional videos are delayed until a site visitor scrolls down the page and additional content comes into view.

By using Lazy Loading, the images/videos are not loaded until needed. This can provide a significant boost in performance for sites that include a lot of high-resolution images and embedded videos.