Image optimization: the questions we get asked most

The advice here is unglamorous, which is probably why it gets skipped. The questions about image optimization that come up most often on our calls.

Speed is a feature people notice only in its absence, and then they leave rather than complain. The version that survives contact with a real deadline is the simple one.

Do we need to care about this?

Images are usually the largest thing on a page. Getting it slightly wrong is survivable. Ignoring it entirely is not. Doing this properly once is usually cheaper than doing it approximately three times.

Can it wait until after launch?

Occasionally. More often the post-launch version costs several times the pre-launch one. None of that requires a large budget, only a decision and someone to own it.

How do we know it is working?

Serving a 3000px image into a 400px slot is pure waste. Small and consistent beats large and occasional here. Anything you cannot measure here, you are deciding by taste, which is fine as long as everyone knows it.

The short version

Performance work is mostly subtraction, which makes it unpopular and effective. Three things worth confirming about image optimization before you move on:

• Someone can say what the current setup is without going to look
• Serving a 3000px image into a 400px slot is pure waste — 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.