When critical CSS is worth the effort

The advice here is unglamorous, which is probably why it gets skipped. Critical CSS is not free, and pretending otherwise leads to bad decisions.

Speed is a feature people notice only in its absence, and then they leave rather than complain. Budget a little time for it every quarter and it never becomes a project of its own.

When it is worth it

Inlining what is needed first shortens time to first paint. None of that requires a large budget, only a decision and someone to own it. Assume whoever inherits this will have half your context and none of your patience.

When it is not

If nothing downstream depends on it and nobody is complaining, it can wait. There is a version of this that is over-engineered, and it is worth avoiding.

How to decide

Only worth the complexity on high-traffic pages. In practice this is a scheduling problem more than a technical one. Budget a little time for it every quarter and it never becomes a project of its own.

In practice

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

If any of that sounds like a description of your current setup, it is fixable.