When image optimization is worth the effort

The version of this that works is simpler than the version most people imagine. Image optimization is not free, and pretending otherwise leads to bad decisions.

Real-world numbers from actual visitors matter more than a score produced on a fast laptop. It rarely shows up as a line item, which is exactly why it slips.

When it is worth it

Images are usually the largest thing on a page. That sounds obvious written down. It is still the thing most often skipped. If two people in the business would answer this differently, that gap is the actual problem.

When it is not

If nothing downstream depends on it and nobody is complaining, it can wait. None of that requires a large budget, only a decision and someone to own it.

How to decide

Serving a 3000px image into a 400px slot is pure waste. Where this goes wrong is almost never a lack of knowledge. The practical test is whether someone new to the project could tell, in a minute, that it had been handled.

In practice

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

If you are not sure where your systems currently stand on this, it takes us about an hour to find out.