Performance Optimization quiz

Test your Performance Optimization knowledge with a free interactive quiz — 50 questions with answers and explanations. No signup needed to play.

Which `<script>` attribute lets the browser continue parsing HTML while the script downloads, and runs the script only after the document is parsed?

1. Which `<script>` attribute lets the browser continue parsing HTML while the script downloads, and runs the script only after the document is parsed?
2. What is "code splitting"?
3. A blocking CSS file is 80 KB and includes both above-the-fold and below-the-fold styles. Best fix?
4. A page has a 2 MB JavaScript bundle. Which is the most effective first fix?
5. Which image format generally yields the smallest size at equivalent quality?
6. Why is `font-display: swap` commonly recommended?
7. Which CSS animation property is GPU-accelerated and cheap to animate?
8. A 3rd-party analytics script blocks the main thread for 400ms during page load. Best mitigation?
9. What does CLS measure?
10. Which `Cache-Control` value is best for hashed static assets?
11. What does `loading="lazy"` on an `<img>` do?
12. Which Core Web Vital measures loading performance?

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