SEO• 5 min read

Core Web Vitals in 2026: The New INP Playbook

We audited 120 sites. Here's what actually moves the needle on Interaction to Next Paint.

WT
WebCodeDev Team
The INP playbook: Interaction to Next Paint, explained

INP replaced FID as a Core Web Vital in March 2024, and by 2026 it's the single biggest ranking signal in the CWV family. We audited 120 sites and found that the same 5 patterns cause 80% of INP problems.

The 5 patterns that kill INP

  1. Heavy hydration — large React trees hydrating on first interaction.
  2. Third-party scripts — especially tag managers with synchronous loads.
  3. Unoptimized images — decoding on interaction rather than eager.
  4. Event handler bloat — multiple listeners on scroll/resize.
  5. Synchronous storage — localStorage writes blocking the main thread.

The playbook

Start with a RUM tool (we use Vercel Analytics or PostHog) to find your worst pages. Then:

  • Move third-party scripts behind next/script with lazyOnload.
  • Use startTransition for non-urgent state updates.
  • Debounce scroll/resize handlers to 16ms.
  • Lazy-load below-the-fold images with native loading="lazy".
  • Replace localStorage with IndexedDB for anything over 10KB.

Teams that follow this playbook typically see INP drop from 400ms+ to under 150ms within a sprint.