Three myths about mobile performance

The gap between knowing this and actually doing it is where most teams lose ground. A few things about mobile performance that get repeated more often than they get checked.

Real-world numbers from actual visitors matter more than a score produced on a fast laptop. Doing this properly once is usually cheaper than doing it approximately three times.

“It only matters for big sites”

Phones have less processing power and worse networks. The reasoning matters more than the rule, because the rule has exceptions. It rarely shows up as a line item, which is exactly why it slips.

“We can deal with it after launch”

Sometimes true, usually expensive. Where this goes wrong is almost never a lack of knowledge.

“Our platform handles it”

JavaScript costs far more on mobile than on desktop. None of that requires a large budget, only a decision and someone to own it. Budget a little time for it every quarter and it never becomes a project of its own.

The short version

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

• Someone can say what the current setup is without going to look
• JavaScript costs far more on mobile than on desktop — 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.