What is Lazy Loading and What Does it Do?

Imagine that you’re on a commute or trip and you’re scrolling through Facebook, trying to kill some time. Now imagine that a friend has pasted a link. You press a little too hard while you’re scrolling through your Facebook feed, and all of a sudden, you’re on a new page. A page filled with images — a photo gallery, maybe — that your friend thought his friends would enjoy, but when you see the first image, you decide maybe it’s not for you and you leave the page.

What is Lazy Loading?
So, what happened when you clicked on the link? Did you load the whole site that you never ended up looking at? If the site uses “lazy loading,” then no, you didn’t. Sites that eat up a lot of data — photo galleries being a good example — enable lazy loading so that they load more quickly and don’t blow all of your data if you end up not looking at them.

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How Does Lazy Loading Work?
Instead of downloading the entire site in one go, which would take a long time for larger sites, your device downloads a series of placeholders that correspond to the actual information on the page. The browser caches all of the site’s resources, but doesn’t actually load them; it simply knows where each one goes. If you end up scrolling through the page, the browser will begin to plug things in right before you get to them. If you’re nearing a placeholder for a picture, the browser finds that picture in its cache and slides it into place. But, if you glance at a page and decide you don’t want to read it, no harm, no foul: you’ve actually only loaded the very top of that page, the part you’ve laid eyes on.

You’ve probably seen this while online. Google’s image search, for example, uses lazy loading, with the thumbnails replacing placeholders as you scroll down the page. Scroll fast enough and you’ll see it in practice.

Lazy Loading Works for Sites and You
So, are websites just being generous, looking out for you, your data, and your time? Not exactly. While lazy loading is actually beneficial to you, it helps the sites out, too. Sites load much faster using lazy loading, which drives traffic. People will give up on a site if it takes forever to appear. If the site can entice the user quickly with the top loaded section, the user is more likely to stick around and allow the rest of the site to load. Ultimately it’s a win-win situation, and an innovative solution to sites with a lot of information.