The New Standard: Why INP Replaced FID

Google’s Core Web Vitals represent crucial ranking signals for organic search. While First Input Delay (FID) only measured the very first interaction on a page, Interaction to Next Paint (INP) tracks the latency of all user interactions throughout the entire page lifecycle.

1. Top Causes of Poor INP on WordPress Sites

  1. Heavy JavaScript Long Tasks (>50ms): Monolithic scripts blocking the main thread.
  2. Excessive DOM Depth: Deeply nested HTML layouts requiring prolonged style recalculations.
  3. Un-throttled Event Handlers: Missing requestAnimationFrame or debouncing on scroll/input listeners.

2. Practical Strategies to Fix INP

  • Break Up Long Tasks: Leverage scheduler.yield() in JavaScript execution loops.
  • Replace jQuery Monoliths: Convert heavy UI plugins to modern, modular vanilla JavaScript.

3. Slashing Time to First Byte (TTFB) & Database Bottlenecks

Aim for a TTFB below 200ms by implementing persistent Redis object caching and cleaning up bloated autoloaded options in wp_options.