Core Web Vitals keep evolving, and most 'SEO checklists' online are still optimizing for metrics that no longer carry the weight they used to.
Interaction to Next Paint (INP) is now the responsiveness metric that matters — not First Input Delay. That changes which parts of your JavaScript bundle actually deserve attention.
In practice, we've found the highest-leverage fix across client sites is deferring non-critical third-party scripts (chat widgets, analytics pixels) until after first interaction, which alone often resolves 60-70% of INP violations.
Layout shift remains the most visually obvious metric to users, and still the easiest to fix: reserve space for images, ads and embeds before they load.