Browser & Web Performance · Junior · Question 7 of 75

Why is CSS called render-blocking?

1CSS files block JavaScript from being downloaded
✓Correct answer: The browser won't render the page until the CSSOM is built, to avoid showing unstyled content
3CSS stops the HTML parser from building the DOM

Explanation

Painting before styles are known would cause a flash of unstyled content. That's why critical CSS should be small and arrive early.

Further reading

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