The performance effects of too much lazy-loading

This post summarizes how we analyzed publicly available web transparency data and ad hoc A/B testing to understand the adoption and performance characteristics of native image lazy-loading. What we found is that lazy-loading can be an amazingly effective tool for reducing unneeded image bytes, but overuse can negatively affect performance. Concretely, our analysis shows that more eagerly loading images within the initial viewport—while liberally lazy-loading the rest—can give us the best of both worlds: fewer bytes loaded and improved Core Web Vitals.