How to lazy load images in Hugo

When I launched the new home for my ebooks at The Valley of Code I didn’t think about my hosting bill, and the impact of loading lots of images for the clients as well.

Since each page is very long (no navigation, that’s the point of them being books rather than articles), one could even be 10MB.

So I decided to fix this problem by lazy loading them, in other words the browser only loads the image when the user scrolls to that image.

It’s a tradeoff, but I’m pretty sure 99% of people that open a page will never even scroll to that image right away.

Problem was.. I no control over the markup! All the content was in Markdown.

But I found out Hugo allows us to override how images are rendered.

Create the file layouts/_default/_markup/render-image.html in your theme with this content:

<img src="{{ .Destination | safeURL }}" alt="{{ .Text }}" loading="lazy" />

This makes the resulting HTML have the loading="lazy" attribute, which lazily loads images.