A practical checklist for render-blocking resources

Most teams know this matters. Fewer have decided who owns it. Run through this the next time render-blocking resources comes up.

Performance work is mostly subtraction, which makes it unpopular and effective. It is worth deciding this deliberately rather than inheriting whatever the last person set up.

The checklist

• Scripts and styles in the head delay the first paint
• Defer anything that is not needed immediately
• Third-party tags are frequent offenders
• Someone is named as the owner
• There is a date to review it again

What it costs to ignore

Scripts and styles in the head delay the first paint. The teams that handle this well are rarely the ones with the biggest budgets. Anything you cannot measure here, you are deciding by taste, which is fine as long as everyone knows it.

The short version

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

• Someone can say what the current setup is without going to look
• Scripts and styles in the head delay the first paint — 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.