How to get lazy loading right
Every audit we run turns up some version of this. The short answer to lazy loading is that it is mostly a sequence of small decisions, not one big one.
Speed is a feature people notice only in its absence, and then they leave rather than complain. It is worth deciding this deliberately rather than inheriting whatever the last person set up.
Why it matters
Only load what is about to be seen. Where this goes wrong is almost never a lack of knowledge. Check it against what you would want a competitor's site to get wrong.
The steps
- Establish what you have today before changing anything
- Never lazy-load the main hero image
- Always reserve the space so nothing jumps
- Write down the decision so the next person does not re-litigate it
Always reserve the space so nothing jumps. Small and consistent beats large and occasional here. The failure mode is not doing it wrong, it is doing it once and assuming it stays done.
Where to go from here
In practice
Performance work is mostly subtraction, which makes it unpopular and effective. Three things worth confirming about lazy loading before you move on:
- Someone can say what the current setup is without going to look
- Never lazy-load the main hero image — and you know whether that is true here
- There is a way to tell whether the last change to this helped
Pick the one that would hurt most if it failed, and start there.