Lazy loading: the questions we get asked most

The version of this that works is simpler than the version most people imagine. The questions about lazy loading that come up most often on our calls.

Performance work is mostly subtraction, which makes it unpopular and effective. The version that survives contact with a real deadline is the simple one.

Do we need to care about this?

Only load what is about to be seen. None of that requires a large budget, only a decision and someone to own it. The teams that stay on top of it are the ones who put it on a calendar rather than a wish list.

Can it wait until after launch?

Occasionally. More often the post-launch version costs several times the pre-launch one. The cost of getting this wrong is rarely visible on the day it happens.

How do we know it is working?

Always reserve the space so nothing jumps. The teams that handle this well are rarely the ones with the biggest budgets. The practical test is whether someone new to the project could tell, in a minute, that it had been handled.

The short version

Speed is a feature people notice only in its absence, and then they leave rather than complain. Three things worth confirming about lazy loading before you move on:

• Someone can say what the current setup is without going to look
• Only load what is about to be seen — and you know whether that is true here
• There is a way to tell whether the last change to this helped

The point is not perfection, it is knowing which of these you have consciously chosen to skip.