Google announced Core Web Vitals 3.0 last quarter. The shift is bigger than the LCP/CLS/INP transition: instead of three lab-style metrics, the new spec introduces perceived smoothness as the headline signal.
What actually changes
Three new metrics replace INP: Hover Response, Scroll Stability, and Long Animation Frames. Together they sample the actual frame timeline rather than synthetic events.
Hover Response
Time from pointer hover to first visual feedback. Critical for menus, tooltips, and interactive cards. Target: under 50ms at p75.
Scroll Stability
Measures jank during scrolling. Replaces CLS for the post-paint window. Sites with heavy IntersectionObserver work tend to fail this one.
What to do this quarter
- Audit hover interactions on your top 5 templates
- Move heavy IO logic off the main thread or batch it
- Switch CWV monitoring to the v3 SDKs