In March 2024, INP replaced which metric as a Core Web Vital?

INP (Interaction to Next Paint) replaced FID (First Input Delay). FID only measured the input delay of the first interaction. INP looks at all interactions and the full delay until the next paint, so it reflects responsiveness much better.

TBT (Total Blocking Time) is a tempting wrong answer. It is a lab metric, measured in tools like Lighthouse, not a Core Web Vital. TTI (Time to Interactive) and FCP (First Contentful Paint) were never Core Web Vitals either.