Interaction to Next Paint: Definition and How It Works

Ritisha

May 26, 2025

Introduction

In the ever-evolving landscape of web performance, Google’s Core Web Vitals have emerged as essential metrics that directly influence user experience and SEO. While metrics like Largest Contentful Paint (LCP) and Cumulative Layout Shift (CLS) have been part of the performance conversation for some time, Interaction to Next Paint (INP) is a relatively new and increasingly important addition.

As digital platforms become more interactive, measuring how quickly a page responds to user input becomes critical. INP addresses this by capturing a more holistic view of interaction latency, filling the gaps left by earlier metrics like First Input Delay (FID).

For businesses, developers, and any reputable digital marketing agency, understanding and optimizing INP is not just about better performance scores—it’s about delivering a smooth, responsive experience that retains users and boosts engagement. In this blog, we’ll dive into what INP is, how it works, and how you can optimize your site to meet this crucial performance metric.

INP (Interaction to Next Paint)- Meaning

Interaction to Next Paint (INP) means a web performance metric introduced by Google as part of the Core Web Vitals suite. It measures the latency of a user interaction—from the moment a user engages with a page element (like clicking a button or typing in a field) to the moment the screen visibly updates in response to that input.

Unlike First Input Delay (FID), which only captures the delay before a browser starts processing an interaction, INP measures the full cycle of interaction, including processing and visual feedback. This makes it a more comprehensive and reliable indicator of how responsive a web page feels.

Google’s Official Definition of INP:

INP is the latency of the interaction that takes the longest, observed during a user’s visit to a page, excluding outliers.

This single metric offers a clearer view of whether users are experiencing sluggish or responsive interactions on your site.

Why Did Google Introduce INP?

INP was introduced to address the shortcomings of FID, which only measures input delay, not the time it takes for the browser to render visual changes after the input. While FID is useful, it often underrepresents the true user experience, especially on modern websites with complex JavaScript operations.

As websites became more dynamic and app-like, Google recognized that measuring just the initial input delay wasn’t enough. A slow update after the user clicks a button can be just as frustrating as a delayed response to that click.

Key reasons for introducing INP:

• Holistic interaction measurement: INP accounts for all phases of interaction, not just the beginning.
• Better user experience assessment: It reflects how fast users see results after input.
• Improved accuracy: INP captures the most meaningful interaction delays across a session.
• SEO relevance: With INP becoming a Core Web Vital, it’s now a potential ranking factor.

How INP Works: A Deep Dive

To understand how INP functions, it’s essential to break down the stages of a typical user interaction on a web page.

1. Input

This is the point at which a user initiates an action—such as clicking a button, pressing a key, or touching the screen.

2. Processing

The browser captures the event and starts executing the associated event handlers. This phase can involve running scripts, performing calculations, and accessing data.

3. Next Paint

Once processing is complete, the browser updates the visual elements in response to the interaction. This could include highlighting a button, displaying a modal, or rendering new content.

INP measures the total time between the start of input and the next paint that reflects the interaction. Importantly, INP focuses on the slowest meaningful interaction during a page visit, which better represents the worst-case user experience.

Key Technical Details:

• INP is calculated in the field, using real-user monitoring (RUM) data.
• It only includes discrete interactions like clicks and keypresses, not scrolling or passive actions.
• Google filters out outliers and ignores short sessions to avoid skewed results.

How to Measure INP

To measure INP accurately, several tools and methods can be used. Understanding your current INP score is the first step toward meaningful optimization.

Tools to Measure Google’s Interaction to Next Paint:

Chrome User Experience Report (CrUX)

• Provides field data based on real users
• Shows percentile distributions of INP and other Core Web Vitals

PageSpeed Insights

• Uses CrUX data for live performance scoring
• Shows your INP score with recommendations

Lighthouse

• Useful for lab testing
• Includes simulated INP under Performance audit

Web Vitals Extension

• Real-time metrics while browsing
• Great for developers testing live changes

JavaScript PerformanceObserver

• For custom tracking and debugging
• Offers precise control over how INP is logged

What Is a Good INP Score?

Google’s recommended INP thresholds:

• Good: Less than 200 ms
• Needs Improvement: 200–500 ms
• Poor: Greater than 500 ms

When you measure interaction to next paint, consistently hitting below 200ms indicates a fast and responsive site.

Factors That Affect INP

Numerous technical and design-related elements influence INP scores. Identifying and addressing these bottlenecks is essential to provide a seamless user experience.

Common INP Performance Bottlenecks:

Long JavaScript Tasks

Scripts that block the main thread prevent the browser from processing input and rendering quickly.

Heavy Third-Party Scripts

Ads, analytics tools, and social widgets can delay processing.

Unoptimized Event Handlers

Inefficient event listeners can lead to slow input responses.

Complex DOM Manipulations

Re-rendering large portions of the DOM slows down visual updates.

Network Latency

Input that triggers data fetching can cause visual delays if not handled asynchronously.

Main Thread Blocking

• Synchronous operations or layout thrashing can halt rendering.
• Understanding these issues is key for any digital marketing agency aiming to fix Core Web Vitals issues and improve site responsiveness to user interactions.

Fixing INP: Practical Optimization Tips

Improving Interaction to Next Paint (Google) requires a mix of JavaScript optimization, design best practices, and modern performance techniques. Here’s a checklist of proven methods:

1. Minimize JavaScript Execution

• Split code into smaller chunks
• Use dynamic imports and tree-shaking

2. Break Up Long Tasks

• Use requestIdleCallback or setTimeout to defer non-critical work
• Use Web Workers for offloading complex logic

3. Optimize Event Handlers

• Keep event handlers lightweight
• Avoid unnecessary DOM reads/writes

4. Prioritize Input Feedback

• Provide immediate visual responses even if the full action takes longer
• Use placeholders or skeleton screens

5. Reduce Main Thread Blocking

• Avoid layout thrashing and synchronous rendering
• Audit and refactor costly DOM operations

Implementing these optimizations is often where technical guidance becomes crucial. Businesses that want to improve Core Web Vitals issues should consider working with specialists to avoid regressions.

INP and Business Impact: Why It Matters

Your INP score is more than just a number—it’s a reflection of how smooth your website feels to users. A site with poor INP frustrates visitors, increases bounce rates, and diminishes conversion opportunities.

From an SEO perspective, INP is now a Core Web Vital, making it a signal in Google’s ranking algorithm. Faster, more responsive pages are not only more enjoyable—they also rank better.

For businesses that rely on conversions, this makes INP a performance and revenue concern. Partnering with a digital marketing agency that understands technical SEO and web performance is a smart step toward long-term success.

Future of INP in Web Performance

INP is more than a passing trend—it represents Google’s direction for more user-focused performance metrics. As web experiences grow more dynamic and JavaScript-heavy, metrics like INP will only become more central.

Future possibilities include:

• INP being adapted or merged into composite UX scores
• Tighter thresholds as user expectations riselo
• Greater emphasis in Google’s ranking factors

Staying ahead means not just meeting today’s standards but preparing for tomorrow’s expectations.

Conclusion

I-N-P is a powerful metric that bridges the gap between user interaction and visual feedback. By understanding how INP works and how it’s measured, businesses and developers can better assess and improve the responsiveness of their websites.

For any business aiming to thrive online, optimizing Interaction to Next Paint is a critical part of the performance puzzle. Regularly monitor your site, refine your code, and stay updated on evolving best practices.

Need help improving your INP score? Hire Core Web Vitals consultants from our expert team to ensure your site delivers fast, seamless, and search-friendly experiences.