Interaction to Next Paint: What to Actually Check on Your Site

Google replaced First Input Delay with Interaction to Next Paint (INP) as an official Core Web Vital in 2024. FID only measured the delay before the first interaction started processing; INP measures the full responsiveness of every interaction on the page — a more honest picture of how a site actually feels to use.

What usually causes a bad INP score

• Heavy JavaScript blocking the main thread during an interaction.
• Too many third-party scripts competing for the same resources.
• Large component re-renders triggered by a single click or tap.

If your site hasn't been checked against INP specifically, it's worth a look — a site can pass the old metrics and still feel sluggish the moment someone actually starts clicking around.