← You Installed a Library for Numbers PerformanceObserver Already Has.Quiz
PerformanceObserver and the Core Web Vitals math
Test what you actually need to know to measure LCP, CLS, and INP natively — and where a naive implementation quietly lies to you.
questions7
pass mark70%
resultsat the end
No account needed. Answer all 7 questions, then see your score with every answer explained and a reference to the spec or MDN — pass and you can claim a certificate.