PerformanceObserver API or PerformancePaintTiming API isn't supported on your browser!

Render Blocking CSS

Try to resize the window's width to than 800px then reload to see how the Render Blocking CSS affects rendering.

The current width is:

Loading events

DOMContentLoaded: ......

Window Loaded: ......

CSS blocked first render: ......


Performance paint timing

NOT BLOCK by CSS BLOCK by CSS
The time to first paint (first render)
The time to first-contentful-paint

For a better understanding:

- Open browser devtool

- Switch to Network tab and select Disable cache

- Switch to Perfomance tab

- Throttle the network to Slow 3G and change CPU to 6x slowdown

You looked at a blank screen for ___ before seeing this