If you've read our earlier guide on optimizing Core Web Vitals, you'll notice it talks about LCP, FID, and CLS. One of those three has quietly retired. Since March 2024, Google replaced First Input Delay (FID) with Interaction to Next Paint (INP) as the third official Core Web Vital — and it's a meaningfully stricter test. If your site was "passing" Core Web Vitals under the old metric, it's worth re-checking, because a lot of sites that sailed through FID are failing INP.
Why Google Made the Switch
FID only measured the delay before the browser started processing your first interaction — a click, tap, or keypress. It ignored everything that happened after that: how long the actual response took, and how long it took the browser to paint the next frame. A page could pass FID with flying colors while still feeling sluggish every time a user clicked a button, opened a menu, or submitted a form.
INP fixes that gap. It measures the full latency of every interaction throughout a page's lifetime, from input to the next visual update, and reports the worst (or near-worst) one. That means a single laggy filter dropdown or a slow-to-respond "Add to Cart" button late in a session can now tank your score — even if your initial page load was lightning fast.
The Thresholds
| Rating | INP Score |
|---|---|
| Good | ≤ 200ms |
| Needs Improvement | 200ms – 500ms |
| Poor | > 500ms |
For comparison, FID's "good" threshold was 100ms — but because FID only measured input delay and not full response time, INP's 200ms is actually a much harder bar to clear in practice for JavaScript-heavy sites.
Why Page Builders Struggle Here Specifically
This is where our earlier point about custom code versus drag-and-drop builders becomes very concrete. Page builder platforms typically load large, generic JavaScript bundles to power every possible widget on the page — accordions, sliders, pop-ups — whether or not you're using them. That JavaScript sits on the browser's main thread, and every one of those idle scripts adds to the delay before your site can respond to a real user interaction.
A lightweight, custom-coded site loads only the JavaScript it actually needs. That's a structural advantage that shows up directly in INP scores, not just in page-load speed.
How We Optimize INP for Client Sites
- Break up long JavaScript tasks. Any task blocking the main thread for more than 50ms delays every interaction behind it. We split large scripts into smaller chunks so the browser can respond to user input between them.
- Defer non-critical JavaScript. Analytics tags, chat widgets, and third-party embeds are loaded after the main content is interactive, not before.
- Avoid layout thrashing on interaction. Reading and writing to the DOM repeatedly within a single event handler forces expensive recalculations — we batch these operations.
- Debounce and throttle expensive handlers. Search-as-you-type fields, scroll listeners, and resize handlers are common INP killers if left unoptimized.
- Reduce hydration cost on JS-framework sites. For React/Vue-based builds, we prioritize partial hydration and code-splitting so the page becomes interactive faster.
- Test with real interaction data, not just lab scores. Lighthouse gives you a lab estimate, but INP is best measured through Chrome User Experience Report (CrUX) field data in Google Search Console, which reflects your actual visitors' devices and networks — critical in markets like ours where a wide range of phone hardware is in daily use.
Checking Your Own Site
Go to Google Search Console → Core Web Vitals report. If you see URLs grouped under "Needs Improvement" or "Poor" for INP, that's real visitors experiencing lag on real interactions — and Google has confirmed Core Web Vitals remain a ranking signal, particularly as a tiebreaker between otherwise similar pages.
The Bottom Line
INP is a stricter, more honest measure of what "fast" actually feels like to a user clicking around your site — not just how quickly the page appeared. For manufacturing and service businesses whose customers are often researching on mobile data in Tier 2/3 cities, this is not a cosmetic metric. It's the difference between a visitor filling out your enquiry form and bouncing before they finish typing.
Not sure where your site stands? Request a free Core Web Vitals audit and we'll send you the actual INP numbers from your real visitor traffic.