Core Web Vitals & INP: The New UX Metrics Google Is Prioritizing

jasdeep singh Reading time: ~7 min October 17, 2025

In 2024, Google officially replaced First Input Delay (FID) with Interaction to Next Paint (INP) as part of the Core Web Vitals suite. If you care about SEO, user experience, and staying ahead of Google’s algorithm updates, mastering Core Web Vitals INP has become essential.

This article delves into what Core Web Vitals are, how INP differs from FID, best practices to measure and optimize, and actionable strategies for 2025 and beyond.

What Are Core Web Vitals?

Google’s Core Web Vitals are a set of standardized metrics that measure key aspects of real-world user experience.

They focus on three dimensions:

Loading performance — how fast content appears (Largest Contentful Paint, or LCP)
Interactivity / responsiveness — how quickly a page responds to user actions (now measured via INP)
Visual stability — how stable the layout is while elements load (Cumulative Layout Shift, or CLS)

Google treats Core Web Vitals as ranking signals under its Page Experience algorithm.

Why Core Web Vitals Matter for SEO & UX

Pages that hit the “Good” thresholds tend to rank better and retain users more effectively.
Poor Core Web Vitals often correlate with high bounce rates and frustrated users.
Google collects field (real user) data via the Chrome User Experience Report (CrUX) to assess how users actually experience pages.
Meeting Core Web Vitals thresholds helps future-proof a site against upcoming algorithm changes.

However, as user expectations evolve, Google recognized limitations with FID (which only measured the first interaction). That’s where INP comes into play.

Introducing INP: What Is Interaction to Next Paint?

Definition & Purpose

INP (Interaction to Next Paint) is the new metric that replaces FID in the Core Web Vitals set. It aims to provide a more holistic measure of responsiveness across all user interactions during a page visit.

While FID measured only the first input delay, INP accounts for:

Input delay — initial event detection to when event handlers start
Processing time — running the event handlers
Presentation delay — time to render (paint) the next frame after a user action
All interactions — not just the first, but every click, tap, or keypress during the lifetime of the page visit

Thus, Core Web Vitals INP gives a better, more representative measure of real-world responsiveness.

How INP Is Calculated

For pages with ≤ 50 interactions, INP is simply the longest observed interaction latency.
For pages with many interactions (> 50), the metric ignores the single worst interaction in each group of 50 interactions, then reports the highest remaining value (to reduce the effect of outliers).
INP is computed at the 75th percentile of visits, similar to how other Core Web Vitals thresholds are measured.

INP is now fully integrated into tools like PageSpeed Insights, Chrome tools, and Search Console.

Good vs Poor INP Values

Google suggests the following thresholds:

Range	Interpretation
≤ 200 ms	Good / “fast” responsiveness
200 ms < INP ≤ 500 ms	Needs improvement
> 500 ms	Poor / unacceptable

The goal is to keep INP under 200 ms for most user interactions to secure a “Good” Core Web Vitals assessment.

Why INP Is More Powerful Than FID

1. Broader Measurement

FID only considered the first interaction and only measured the delay until the event handler begins. It ignored later interactions and the rendering delay. INP, by contrast, tracks every interaction’s full latency, giving a more accurate picture of responsiveness.

2. Realistic User Experience

Users rarely interact just once. Most web sessions involve multiple taps or clicks (menus, buttons, forms). INP treats these real user flows as first-class signals.

3. Encourages Better Code Practices

Because INP factors in event handling and rendering, developers must minimize long tasks, optimize JS execution, and yield control back to the browser more frequently. This enforces more consistent responsive performance.

4. Better SEO Alignment

Google now treats INP as the official interactivity metric in Core Web Vitals, replacing FID.
Thus optimizing Core Web Vitals INP is vital to maintaining or improving your Search rankings.

How to Measure INP & Core Web Vitals

To optimize, you must first measure real performance. Here are key tools and strategies:

Field Data (Real User Monitoring, RUM)

Chrome User Experience Report (CrUX): captures INP from actual users.
Search Console — Core Web Vitals Report: now displays INP performance for your pages.
RUM libraries (e.g. using web-vitals.js, or proprietary performance analytics tools) to capture interaction metrics per user.

Lab & Synthetic Testing

PageSpeed Insights, Lighthouse, and Chrome DevTools will now evaluate INP instead of FID.
WebPageTest or DebugBear: simulate user interactions and reveal slow event handlers and rendering delays.
Use the Event Timing API in instrumentation to capture interaction metrics in a controlled environment.

Note: Lab tools may not fully replicate all user interactions. Thus, field data is critical.

Best Practices to Optimize Core Web Vitals & INP

Improving INP (and other Core Web Vitals) requires a holistic approach across code, architecture, and design. Here are actionable strategies:

1. Break Up Long Tasks

JavaScript operations that block the main thread for long durations (>50 ms) can delay interaction responsiveness. Use techniques like:

Splitting big functions into smaller async chunks
Leveraging web workers
Using requestIdleCallback or scheduling lower priority tasks
Deferring nonessential JavaScript

2. Prioritize Critical Event Handlers

Ensure that key interactive elements (buttons, forms, menus) have lightweight, fast event handlers. Avoid heavy computations or synchronous operations in those handlers.

3. Use Passive Event Listeners

For scroll, touch, and wheel events, use { passive: true } to allow the browser to process events without blocking.

4. Defer or Lazy Load Noncritical JS

Only load scripts when needed, asynchronously or after initial load so they don’t block interaction.

5. Yield to Browser / Break Up Rendering

When doing complex layout or UI updates, break them into smaller slices, giving the browser time to update and paint between chunks.

6. Optimize Third-Party Scripts

Third-party widgets (chat, analytics, ads) often add long tasks. Monitor them carefully, and consider delaying or partially loading them to avoid harming INP.

7. Reduce Layout Thrashing

Excessive, forced synchronous layout recalculations (e.g. reading layout values immediately after writes) can hinder responsiveness. Batch reads & writes wisely.

8. Prioritize UI Feedback

Even minimal visual feedback (e.g. a pressed state) after a user action reassures users the interaction occurred. This helps even when full processing is pending.

9. Monitor & Audit Frequently

Use performance profiling (Chrome DevTools performance tab, Lighthouse audits), record long tasks, and correlate them with user interaction delays.

10. Use Efficient Rendering Patterns

Virtualization, windowing (for long lists), incremental updates, and avoiding unnecessary re-renders help keep interactivity fast.

Integrating INP with Other Core Web Vitals

Optimizing for INP should not come at the expense of LCP or CLS. A balanced strategy is required:

LCP (Loading): optimize server response time, preconnect, preload main resources, and reduce render-blocking CSS/JS.
CLS (Stability): reserve space for images, ads, embed elements; avoid dynamically inserting content above existing ones.

Always test changes holistically to ensure you don’t inadvertently regress LCP or CLS while improving INP.

Monitoring & Maintenance (2025 and Beyond)

Regularly check the Core Web Vitals report in Search Console, focusing on INP alongside LCP and CLS.
Employ Real User Monitoring to capture trends in INP over time.
When you introduce new features (widgets, scripts), test for INP regressions early.
Use performance budgets and enforce them in CI/CD pipelines.
Stay updated: Google may evolve the Core Web Vitals over time (just like replacing FID with INP).

Case Study / Hypothetical Example

Imagine an e-commerce site where the “Add to Cart” button sometimes takes 300 ms to visually respond. This could push the page’s INP above 200 ms, causing a “Needs Improvement” rating and hurting user trust.

By refactoring the button’s click handler to separate UI feedback (immediate class toggle) and deferred logic (AJAX call) and moving heavy logic off the main thread, the site reduces the worst-case interaction latency to around 120 ms — improving INP score and user satisfaction.

Summary & Action Plan

Core Web Vitals INP is now the official Google metric for user interactivity and responsiveness, replacing FID.
It captures the latency of all user interactions, not just the first, making it a more accurate UX measure.
To optimize INP, focus on breaking up long tasks, efficient event handling, yielding to the browser, and minimizing third-party script impact.
Always measure using both real user data and lab tools.
Remember: INP is one piece of the Core Web Vitals puzzle — balance it with LCP and CLS for best results.

By mastering Core Web Vitals & INP, you’ll be well-positioned to deliver superior user experiences and maintain strong SEO rankings in 2025 and beyond.