Signs it is time to revisit critical CSS

Teams tend to reach for this after something has already gone wrong. A few signals that critical CSS is due some attention.

Speed is a feature people notice only in its absence, and then they leave rather than complain. If two people in the business would answer this differently, that gap is the actual problem.

The signals

• Nobody can say when it was last reviewed
• The answer depends on who you ask
• Inlining what is needed first shortens time to first paint
• The rest can load without blocking

Where to start

Only worth the complexity on high-traffic pages. The cost of getting this wrong is rarely visible on the day it happens. Doing this properly once is usually cheaper than doing it approximately three times.

How to tell if yours is fine

Real-world numbers from actual visitors matter more than a score produced on a fast laptop. Three things worth confirming about critical CSS before you move on:

• Someone can say what the current setup is without going to look
• The rest can load without blocking — 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.