Performance Optimization quiz

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

A 3rd-party analytics script blocks the main thread for 400ms during page load. Best mitigation?

1. A 3rd-party analytics script blocks the main thread for 400ms during page load. Best mitigation?
2. What does `<img srcset="img-1x.jpg 1x, img-2x.jpg 2x">` accomplish?
3. When should `<link rel="preload">` be used?
4. Which CDN benefit matters most for global LCP?
5. What does `loading="lazy"` on an `<img>` do?
6. Which `<script>` attribute lets the browser continue parsing HTML while the script downloads, and runs the script only after the document is parsed?
7. What is "code splitting"?
8. Which Core Web Vital measures loading performance?
9. Which metric replaced FID as the Core Web Vital for interactivity in 2024?
10. What does the Lighthouse "performance" score primarily measure?
11. What does enabling Brotli compression on the server give you?
12. A blocking CSS file is 80 KB and includes both above-the-fold and below-the-fold styles. Best fix?

More quizzes