Your site being "fast" isn't enough on its own anymore; Google now measures how quickly a page responds to clicks. That metric is called INP, and most sites still fail to clear the bar. Here is what changed in how it's measured and where to start fixing it.
Three metrics, a quick refresher
Core Web Vitals is made up of three metrics: LCP (Largest Contentful Paint — how long the main content takes to render, target: under 2.5 seconds), CLS (Cumulative Layout Shift — how much the page shifts while loading, target: under 0.1), and INP (Interaction to Next Paint — how long it takes the screen to update after a click or tap, target: under 200 milliseconds).
From FID to INP: what's different
The old metric, FID, only measured the delay before the browser started processing an interaction. INP measures the full latency of the slowest interaction across the entire lifetime of the page, from tap to visible update. That difference matters: many sites that passed comfortably under FID fail INP when measured with real user data, scoring north of 400 milliseconds.
Why most sites struggle with INP
Three things usually hurt INP: heavy JavaScript that keeps the browser's main thread busy, third-party scripts outside the page's own control (ads, analytics, live-chat widgets), and event handlers that do too much work right after a click. The result: a user taps a button and the screen feels unresponsive for a few hundred milliseconds.
Photo: Gunther Samson / Unsplash
What actually moves the needle
- Break large JavaScript tasks into smaller chunks so the browser can pause and respond to interactions in between.
- Defer or lazy-load third-party scripts, loading them only once a user actually interacts with the page.
- In event handlers, update the visible UI first and push background work (like sending analytics) to afterward.
- Strip out unused code and libraries you don't actually need.
How to measure it
PageSpeed Insights and Chrome DevTools give you lab data, but what actually decides the outcome is real-user data (the CrUX report, the Core Web Vitals section in Search Console). A page that looks great in a lab test can behave very differently on a real user's slow device and weak connection.
In short
Think of page speed not just as load time, but as how responsive it feels to a click. We build this into our performance and web development work — if you'd like us to look at your site's INP score together, get in touch.