A man is laughing while experiencing a colorful layout shift with colored powder.

Measuring Interaction And Next Paint

Interaction To Next Paint

A man is laughing while insteracting with next paint and a colorful layout shift.

Measuring Interaction & Next Paint

By: Simon | Category: Pagespeed
Published Date: 9th January, 2024

In the digital age, where users expect instant access to information, website performance plays a crucial role in determining user satisfaction. Google PageSpeed Insights is a powerful tool that helps web developers and site owners analyse and optimise their website’s performance.

Two key metrics that significantly impact user experience are interaction and next paint. In this article, we will delve into the importance of these metrics and explore how to effectively measure and improve them using Google PageSpeed Insights.

Remember, this will be a Core Web Vitals standard metric from March 2024, replacing FID and it will effect your future pagespeed scores.

Understanding Interaction & Next Paint


Interaction refers to the time it takes for a web page to become fully interactive, allowing users to engage with its elements seamlessly. It is a critical metric as it directly influences user engagement and satisfaction. Slow interaction times can lead to frustrated users who may abandon a site before it fully loads or responds to their inputs.

Measuring interaction in Google PageSpeed Insights involves analysing various factors, such as:

Time to Interactive (TTI)

TTI is the moment when a web page is fully interactive, allowing users to click buttons, fill forms, and engage with dynamic elements. Google PageSpeed Insights calculates TTI based on the time it takes for the main thread to become idle after the page has started loading.

First Input Delay (FID)

FID measures the time it takes for a user to interact with a page for the first time, such as clicking a button or selecting an option. It is a crucial aspect of interaction, and a lower FID indicates a more responsive experience.

It’s Not The Images

It’s How Quick It Can Load

After The JS Has Activated

Next Paint

Next paint focuses on the visual aspects of a web page, specifically the time it takes for content to become visible. A quick next paint ensures that users perceive a fast-loading website, contributing to a positive user experience.

Key Elements Of Next Paint Include

First Contentful Paint (FCP)

FCP measures the time it takes for the browser to render the first piece of content on the page. It provides insights into how quickly users see something meaningful, even if the entire page is not yet fully loaded.

Largest Contentful Paint (LCP)

LCP measures the time it takes for the largest content element to become visible to users. Google considers an LCP of 2.5 seconds or less as good, indicating a fast-loading page.

Measuring Interaction And Next Paint With Google PageSpeed Insights

Now that we understand the significance of interaction and next paint, let’s explore how to measure these metrics using Google PageSpeed Insights.

One common cause of CLS is the inclusion of images and media elements without specified dimensions. When these elements load, they may cause the layout to shift as the space required for them is allocated dynamically. Specifying width and height attributes for images allows browsers to reserve the required space, reducing the likelihood of layout shifts.

Now that we understand the significance of interaction and next paint, let’s explore how to measure these metrics using Google PageSpeed Insights.

Accessing Google Pagespeed Insights

Visit the Google PageSpeed Insights website and enter the URL of the web page you want to analyse. Click on the “Analyze” button to initiate the assessment.

Reviewing The Results

Google PageSpeed Insights will provide a comprehensive report on your website’s performance, including scores for both mobile and desktop versions. Focus on the “Field Data” section, which represents real-world user experiences, and the “Lab Data” section, which simulates user interactions.

Analysing Interaction Metrics

Under the “Lab Data” section, you will find metrics related to Interaction, including TTI and FID. Google PageSpeed Insights will provide recommendations to improve these metrics. Common strategies include optimising JavaScript execution, deferring non-essential scripts, and reducing render-blocking resources.

Examining Next Paint Metrics

To assess next paint metrics, focus on FCP and LCP under the “Lab Data” section. If these metrics are not meeting the desired thresholds, consider optimising images, leveraging browser caching, and prioritising critical CSS to expedite rendering.

Utilising Opportunities And Diagnostics

Google PageSpeed Insights offers an “Opportunities” section that provides specific suggestions for improvement. This may include optimising images, leveraging browser caching, or eliminating render-blocking resources. The “Diagnostics” section further identifies potential issues affecting performance.

Improving Interaction & Next Paint

Optimise Images

Large image files can significantly impact both interaction and next paint metrics. Use image compression tools to reduce file sizes without compromising quality. Additionally, consider implementing lazy loading for images, ensuring they load only when they become visible to the user.

Minimise Render-Blocking Resources

Render-blocking resources, such as JavaScript and CSS files, can delay the rendering of a page. Optimise and minimise these resources by deferring non-essential scripts and using asynchronous loading where possible. This allows critical content to load faster, improving both interaction and next paint.

Leverage Browser Caching

Enable browser caching to store static resources locally on users’ devices. This reduces the need for repeated downloads of the same resources on subsequent visits, leading to faster load times. Browser caching is particularly effective in improving next paint metrics.

Prioritise Critical CSS

Critical CSS contains the styles necessary to render above-the-fold content. By prioritising the loading of critical CSS, you ensure that users see meaningful content quickly. This directly contributes to a faster FCP and improved user perception of your website’s speed.

Evaluate Third Party Scripts

Review and assess the impact of third party scripts on your website’s performance. Limit the use of unnecessary third party scripts and consider asynchronous loading to prevent them from blocking the rendering of critical content.

Implement Code Splitting

Code splitting involves breaking down large JavaScript files into smaller, more manageable chunks. This allows the browser to load only the essential code required for the current page, enhancing TTI and reducing FID.

Monitor Server Response Times

Slow server response times can significantly affect both Interaction and next paint. Regularly monitor server response times and optimise server configurations, utilise content delivery networks (CDNs), and ensure efficient server-side processing to improve overall performance.

My Conclusions

By understanding the significance of TTI, FID, FCP, and LCP, and implementing strategic improvements, you can create a faster, more responsive website that leaves a positive impression on your users. Regularly analyse your site’s performance, address identified issues, and stay committed to providing a seamless and enjoyable online experience for your audience.

Technial blog author

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