Interaction to Next Paint (INP) is a user-centric metric for measuring website responsiveness. It gauges the time from when a user first interacts with a page, like clicking a link or tapping a button, to the moment the browser starts updating the display in response.

This metric holds vital importance as it directly correlates to user experience; users typically favour sites that respond swiftly and smoothly to their inputs.

Understanding and improving INP can lead to better user engagement and satisfaction. Websites that react quickly to user input provide a more seamless and enjoyable journey, making users more likely to stay on the page, engage with content, and complete important tasks such as purchases or sign-ups.

For developers and website owners, optimising for INP can be crucial in creating a competitive and successful online presence.

Your website’s performance in terms of INP can also affect search engine rankings as search engines consider page responsiveness as a factor for SEO.

Therefore, monitoring and enhancing INP should be a key aspect of your site’s performance optimization strategy. This involves taking a close look at elements that can delay painting, such as heavy JavaScript execution or resource-intensive tasks, and finding ways to minimise their impact.

Interaction to Next Paint and Core Web Vitals

On March 12, the Web Vitals initiative by Google will undergo a significant update. Interaction to Next Paint (INP) will be introduced as a Core Web Vital, taking over from First Input Delay (FID). This change signifies Google’s commitment to refining how it measures user experience on web pages.

INP offers a more precise measurement of interactive responsiveness. It records the duration from a user’s interaction, such as clicking a button, to the moment when the browser is capable of updating the display with the new changes.

Unlike FID, which only captured the delay for processing an input, INP provides a fuller picture of the user’s experience.

How to Prepare

To adapt to this update, follow these recommendations:

  • Evaluate Performance: Utilise tools like PageSpeed Insights or Chrome User Experience Report to assess how your site fares with INP.
  • Identify and Fix Issues: Look for factors negatively affecting INP, such as extensive JavaScript operations, excessive main thread usage, or bulky DOM.
  • Optimise: Based on your findings, enhance your site performance. This could involve optimising JavaScript, reducing input lag, and simplifying your site’s DOM structure, among other technical improvements.
What is Interaction to Next Paint (INP): Decoding Core Web Vitals

Impact on Web Development

The adoption of INP as a Core Web Vital could lead to shifts in web development practices. Your site’s INP score may begin to influence search rankings and user interaction levels.

As Google includes Core Web Vitals in its algorithm, achieving a “good” INP benchmark — performance at the 75th percentile of page loads — will be increasingly crucial.

To ensure readiness for the switch to INP, developers should now prioritise areas that affect interactivity, potentially ushering in changes to application architecture and coding practices. Performance monitoring tactics and the tools you rely on will also need to adapt to accommodate INP analysis.

Understanding Interaction to Next Paint (INP)

Interaction to Next Paint (INP) is a user-centric metric for measuring responsive load-time interactions on web pages. It focuses on quantifying the user experience by highlighting how long it takes for a web page to respond to user interactions.

Unlike other metrics that measure the visual completeness of a page, such as First Contentful Paint (FCP) which registers the time when the first text or image appears, and Largest Contentful Paint (LCP) which notes when the largest content element becomes visible, INP captures the user’s interactive experience.

INP is fundamentally different from Time to Interactive (TTI), which denotes the point where a page becomes fully interactive. While TTI indicates when a page can reliably respond to user input, INP offers a more granular measurement by focusing on responsiveness during the loading phase.

It actively measures the delay between a user’s interaction—like clicking a link or button—and when the response to that interaction is painted on the screen.

To calculate INP, the browser notes the delay of discrete user inputs during load-time and captures the delay of the event that takes the longest to process and present on the screen.

This approach provides insights into the specific points where user experience might be hindered due to excessive processing times, thus allowing developers to optimise the interactive readiness of web pages.

Key Takeaways:

  • INP gauges responsiveness from a user’s perspective.
  • It is distinct from FCP, LCP, and TTI, focusing on the interactive experience.
  • It measures the longest delay to a user’s input during loading.
  • Provides actionable data to improve web performance.
What is Interaction to Next Paint (INP): Decoding Core Web Vitals

Why INP Matters

When you browse websites, your experience hinges on how fast and responsive the page feels to your interactions. Interaction to Next Paint (INP) measures the responsiveness of a website by quantifying the time from when you interact with the page to when the browser renders the pixels reflecting the response to your interaction.

A solid INP score is imperative for a satisfactory user experience. If the INP is subpar, you may perceive the site as sluggish, which can lead to frustration and potentially cause you to leave the page. High responsiveness equates to a perception of instantaneous feedback, which keeps you engaged and satisfied.

Moreover, INP influences your site’s performance in search engine rankings. Search engines, like Google, consider page experience signals in their ranking algorithms.

If a website demonstrates a high INP score, it suggests to these engines that visitors are likely having a favourable experience. Consequently, this can contribute to better visibility and higher rankings in search results.

A website’s success is closely aligned with how users perceive its performance. By ensuring a website has a favourable INP score, you enhance not only user satisfaction but also the potential for increased traffic and improved search engine rankings.

Therefore, paying attention to INP is a direct investment in the user experience and the overall success of a website.

How to Measure INP

To accurately assess Interaction to Next Paint (INP), various tools and techniques are available. Notable among these are the Chrome User Experience Report and the web-vitals library.

The former provides real-world user experience data gathered from individuals using Chrome, while the latter is a JavaScript library designed for measuring web performance, including INP.

Getting Started with Tools

  1. Chrome User Experience Report
    • Access the report through Google BigQuery.
    • Filter the dataset for your specific website.
    • Query the experimental_interaction_to_next_paint metric for observations.
  2. Web-vitals Library
    • Install the library via npm npm install web-vitals or include it directly in your webpage.
    • Integrate the library in your site’s code.
    • Set up event listeners to capture INP data.

Measuring INP Steps

Process for Chrome User Experience Report

  • Review the dataset in BigQuery.
  • Extract INP data for your site.
  • Analyse the data using SQL queries.

Process for Web-vitals Library

  • Install and implement the web-vitals library in your site.
  • Use getINP() function to measure INP.
  • Collect and log this data for further analysis.

Remember to consistently check for the latest metric definitions and library updates to ensure the most accurate measurements. By following these processes, you can obtain your website’s INP score and work towards enhancing the user experience.

The proper use of INP measurements can guide optimisation strategies for your website’s interactivity and responsiveness.

Improving Your Site’s INP Score

To elevate your site’s Interaction to Next Paint (INP) score, focus on streamlining user interaction handling and optimising code execution times. Begin by scrutinising your JavaScript execution since it’s often the primary culprit in delaying interactions.

Prioritise Critical JS: Load only the essential JavaScript needed to enable user interaction initially, deferring less critical scripts.

Minimise Main Thread Work: Keep tasks on the main thread as short and non-blocking as possible, reducing time spent parsing, compiling, and executing scripts.

Optimise Asset Loading: Implement lazy loading of images and offscreen iframes, which can lower initial load times, leading to quicker first interactions.

Employ Efficient CSS: Avoid complex CSS selectors which can slow down rendering; aim for simplicity in your design where feasible.

Utilise Web Workers: Offload tasks to web workers to process computations in the background, preventing interference with the user interface thread.

Enhance Response Times: For any user inputs, ensure your site’s backend responds swiftly. Delays in server responses directly impact INP scores.

Regularly Monitor Performance: Employ tools like Chrome DevTools and Lighthouse to continuously monitor your site’s performance metrics, including INP. Audit frequently and iterate upon the feedback provided.

Remember, your users’ perception of speed improves with a better INP score. Swift interactions foster a sense of smoothness and responsiveness, crucial for a positive user experience. Implement these strategies systematically and you should see a progressive enhancement in your website’s responsiveness and overall performance.

What’s a good Interaction to Next Paint value?

When assessing the performance of a web page, the metric Interaction to Next Paint (INP) is vital. A good INP value is indicative of a responsive and user-friendly website.

Target INP: A superior INP value is generally below 200 milliseconds. This threshold suggests that the site responds quickly to user inputs, providing a seamless browsing experience.

Acceptable INP Range:

  • Excellent: Less than 100 ms
  • Good: 100-200 ms
  • Fair: 200-500 ms
  • Poor: More than 500 ms

The aforementioned ranges are widely recognised standards in web performance. Staying within these parameters typically ensures that the majority of users find the interaction response times to be satisfactory.

INP and User Experience:

  • Quick interactions (< 100 ms): Users perceive immediate responses, enhancing their interaction with the site.
  • Moderate interactions (100-200 ms): Users experience slight delays, but generally remain engaged with the site content.
  • Noticeable delays (200-500 ms): Delays begin to interrupt the user’s workflow, potentially leading to frustration.
  • Long delays (> 500 ms): These are likely to be disruptive, negatively affecting the user’s perception of the site.

It is also important to note that different types of interactions may have varying INP targets. For instance, typing is usually less sensitive to latency than tapping a button. Tweaking and optimising your web pages to aim for the best INP value possible will vastly improve the user’s experience on your site.

How is Interaction to Next Paint different from First Input Delay?

Interaction to Next Paint (INP) and First Input Delay (FID) are both metrics for measuring user experience, but they focus on different aspects of the interaction. INP measures the responsiveness of a web page throughout the user’s visit, not just the first input.

It captures the delay between an interaction, like clicks or key presses, and when the browser can update the visual response to that interaction.

  • INP:
    • Takes into account the entire duration of a page visit.
    • Reflects the experience of users during subsequent interactions after the page has loaded.
  • FID:
    • Is limited to the first input from the user.
    • Does not provide information on the page’s performance after the initial interaction.

INP is considered a more comprehensive measure when assessing the ongoing interaction quality a user experiences with a web page. Its introduction moves the focus towards understanding and improving the interactivity of web pages over time.

It’s useful to look at both INP and FID to get a complete picture of a page’s interactivity performance, as they complement each other by highlighting different interaction phases.

Challenges and Considerations

  • Common challenges: Your work with Interaction to Next Paint (INP) may encounter issues such as varied user behaviours and diverse device capabilities. To manage these, continually monitor performance and adopt responsive design strategies prioritising user experience.
  • Balancing content and performance: Ensure your website’s performance isn’t compromised by its features. As you introduce rich content, use techniques like lazy loading and asynchronous script loading to maintain balance.
  • Future of web metrics: Stay informed about updates to web performance metrics as they evolve. INP’s role is set to grow, so integrate this metric into your performance analysis to remain ahead.

Optimising for Better INP

Improving your Interaction to Next Paint (INP) can significantly improve user experience on your web page. Here are strategies you can implement to optimise INP:

  1. Prioritise Critical Resources: By deferring loading of non-critical resources, you can speed up the time to first interaction. Use lazy loading for images and asynchronous loading for JavaScript files that are not immediately necessary.
  2. Minimise JavaScript Execution Time: Heavy JavaScript tasks can block the main thread, leading to a poor INP. Break up long tasks into smaller chunks and use web workers for off-thread computation.
  3. Enhance Response Animation Idle Load (RAIL) Practices: Factor in RAIL guidelines while developing interactive web apps. Aim for responses within 100ms during actions to ensure a seamless feel.
  4. Optimise Asset Sizes: Compress images and vector graphics, minify CSS and JavaScript, and use modern image formats like WebP to reduce file sizes without losing quality.
  5. Reduce Render Blocking Resources: Inline critical CSS and defer non-critical ones to prevent them from delaying the painting of your page’s content.
  6. Profile and Monitor Performance: Regularly profile your web application’s performance using tools such as Lighthouse and Chrome DevTools. Monitor your INP and other Core Web Vitals to identify areas for improvement.

By incorporating these tactics into your development process, you can achieve better INP scores, leading to a smoother and more responsive user experience on your website.

What is Interaction to Next Paint (INP): Decoding Core Web Vitals

How to Identify INP Problems on Your Website?

Identifying Interaction to Next Paint (INP) issues involves a multi-step process. INP is a metric that measures user interactions and the time it takes for the browser to respond with a visual update.

Step 1: Collect Data Start by using web performance monitoring tools such as Chrome User Experience Report or other web vitals tools to gather data on your site’s performance. This data should include INP metrics.

Step 2: Analyse User Interactions Review the interactions on your site that may affect INP, such as clicks, taps, or key presses. Look at the events that have high response times.

Step 3: Focus on the 98th Percentile INP is measured at the 98th percentile of interaction latencies. Sort your interactions by their response times and pay close attention to the ones in the highest 2%.

Step 4: Pinpoint Specific Pages Determine which pages on your website are experiencing high INP times. This helps you understand where to target your optimisation efforts.

Step 5: Check for Correlation Look for a correlation between high INP times and other performance metrics like First Input Delay (FID) or Total Blocking Time (TBT).

Step 6: Prioritise and Optimise Based on your findings, prioritise the interactions and pages that need improvement. Implement performance optimisation strategies such as code splitting, lazy loading, or improving server response times.

Step 7: Monitor Changes After making optimisations, continue monitoring INP values to track improvements. Regular performance checks ensure ongoing optimal user experience.

Use this structured approach to maintain and enhance the promptness of your site’s responsiveness to user interactions.

The Future of Web Metrics and INP

Interaction to Next Paint (INP) is an emerging metric that measures a user’s experience on a web page. As web technologies evolve, the way we evaluate user interaction continues to improve. INP is gaining attention as a user-centred metric focusing on the responsiveness of a web page to user inputs.

Understanding INP: The core of INP lies in its ability to measure the delay between a user’s interaction, like clicking a button, and the visual response of the web page. Traditional metrics, such as First Contentful Paint (FCP) or Largest Contentful Paint (LCP), capture the loading experience but do not reflect how a page responds under interaction. INP fills this gap.

Brief History: Prior metrics aimed to measure load performance and visual stability, like Cumulative Layout Shift (CLS). However, INP is reflective of the real-world usability of a web site.

Future Adaptations: Web developers may prioritise different metrics for different sites, but INP’s significance is growing. Frameworks and tools are likely to evolve to integrate INP analysis more effectively, helping developers improve the interactive aspects of websites.

Potential Challenges: The challenge in broad adoption of INP lies in standardisation and browser support. As the web community converges on the importance of interactivity, expect updates and broader acceptance of INP norms.

Conclusion: INP’s role in web performance evaluation is set to expand. Its incorporation into performance budgets and best practices signifies its value in constructing user-friendly web experiences. As we move forward, monitoring INP will be crucial in creating fast, responsive websites.


Interaction to Next Paint (INP) is a critical metric for measuring user experience on websites. By focusing on the responsiveness of a page to user interactions, it provides valuable insights into the perceived speed and fluidity of a site.

Effective use of INP can lead to improved user satisfaction, as it prioritises interactivity, which is often a key factor in retaining users’ attention.

  • Responsiveness: High INP scores indicate a site that responds rapidly to user input, enhancing the perception of a seamless experience.
  • Optimisation: Lower INP values suggest a need for optimisation, often achievable through code refinement and reviewing resource-heavy scripts.
  • User Experience: Continuous monitoring of INP helps maintain an engaging user interface, contributing to overall satisfaction.

Improving a site’s INP is an ongoing process involving assessment of script execution times, minimisation of heavy processing tasks, and efficient event handling. You can initiate performance gains by auditing current INP scores and identifying areas for adjustment.

Ensuring High Performance:

  • Maintain efficient code.
  • Prioritise user-centric performance metrics.
  • Assess and optimise regularly.

You can interpret INP as a measure to prioritise in the pursuit of delivering a user-friendly website. It helps form a foundation for assessing and enhancing the interactivity and responsiveness of web content. This focus can ultimately lead to better engagement, retention, and conversion rates.

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