Google's INP Metric: Why Fast Websites Can Still Feel Slow

Why Can a Website Load Fast but Still Feel Slow?

Website speed is often judged by how quickly a page becomes visible, but a visitor's experience doesn't end when the page finishes loading. Think about an e-commerce website. A customer opens a product page, selects a size, and clicks 'Add to Cart'. If the button doesn't respond immediately, they may click it again, wondering whether their first attempt worked.

A similar problem can happen on a service website when someone opens a dropdown menu or submits a contact form. These delays reveal why website speed matters beyond loading time. Visitors expect a website to respond when they interact with it, not just appear quickly on their screens.

Two aspects of performance matter here:

• Loading performance: How quickly does the website display its content.
• Interaction responsiveness: How quickly the website visually responds after a visitor clicks, taps, or types.

What Does Interaction to Next Paint (INP) Actually Measure?

Interaction to Next Paint (INP) is one of Google's three Core Web Vitals, alongside Largest Contentful Paint (LCP) and Cumulative Layout Shift (CLS). While LCP measures loading performance and CLS measures visual stability, INP evaluates how responsive a webpage is to user interactions. For example, when someone clicks a button, INP measures the time between that action and the browser's next visual update.

According to Google's official INP documentation, the performance thresholds are:

Google evaluates these scores using real-user experience data, focusing on the 75th percentile of page visits. But what actually happens between a click and the website's response?

1. Input Delay: The browser takes time before it can start processing the action.

2. Processing Time: The website runs the instructions required to handle the interaction.

3. Presentation Delay: The browser prepares and displays the next visual update.

For example, an interaction might spend 70 milliseconds waiting, 180 milliseconds processing, and 100 milliseconds displaying the result. That creates a total delay of 350 milliseconds. The visitor doesn't see these individual stages. They simply experience a button that feels slow.

Why Can a Website Have a Good PageSpeed Score but Poor INP?

A good Google PageSpeed Insights score doesn't automatically mean every interaction on a website is fast. PageSpeed Insights combines laboratory testing with real-user performance data when available. Its Lighthouse performance score primarily evaluates how a page behaves during a controlled loading test. However, real visitors do much more than load a webpage. They explore product categories, type into search fields, open menus, and interact with forms.

A page may perform well during the initial test, but experience delays when those interactions happen. For instance, a travel booking website might display its homepage quickly. Yet selecting dates or applying multiple filters could trigger heavy processing that makes the interface temporarily unresponsive. This is why businesses should examine website responsiveness alongside loading metrics rather than relying on one overall performance score.

What Causes a Poor INP Score?

A high INP score usually indicates that the browser is spending too much time waiting, processing an action, or preparing the next visual update. Several common website issues can contribute to this problem.

Heavy JavaScript Execution

JavaScript powers interactive website features such as filters, forms, animations, and dropdown menus. However, when too much JavaScript runs at once, the browser may be occupied with other work instead of responding to a visitor's click.

Too Many Third-Party Scripts

Analytics tools, chat widgets, advertising tags, and other integrations can add processing work. These tools are often useful for business operations, but poorly managed scripts may compete for the browser's resources and delay interactions.

Complex Website Elements

Large menus, complicated page layouts, and product listings with numerous interactive elements can require substantial rendering work. For example, a product filter that updates hundreds of items unnecessarily may take longer to display the next screen.

Inefficient Interaction Handling

Sometimes the delay comes from the code running after a button is clicked. If a form performs lengthy calculations or updates too many website elements before displaying feedback, visitors may experience a noticeable pause.

However, not every slow feature is necessarily an INP problem. A server response can take time even when the website immediately displays a loading indicator. Accurate diagnosis requires checking where the delay occurs.

Does Google's INP Metric Affect SEO Rankings?

Yes, INP is part of Google's Core Web Vitals, which are considered by Google's ranking systems as part of overall page experience. Google replaced First Input Delay (FID) with INP in March 2024 because FID measured only part of the responsiveness experience, whereas INP provides a broader view of interactions throughout a page visit. However, a better INP score doesn't guarantee higher search rankings.

Google also considers content relevance, usefulness, and other signals. A technically fast website with unhelpful content is not automatically more deserving of a higher position. For businesses, the value of improving responsiveness also extends beyond SEO.

A delayed menu can interrupt navigation. An unresponsive form can create uncertainty about submission. A slow checkout interaction can make an otherwise straightforward purchase frustrating. This reinforces why website speed matters for both search visibility and the customer experience.

How Can You Check Your Website's INP Score?

If you're asking "why is my website slow" despite good loading results, start by measuring what real visitors experience. Several tools can help identify the problem.

Google PageSpeed Insights

Enter your website URL into PageSpeed Insights and check the real-user performance section. When sufficient data is available, it displays INP alongside other Core Web Vitals.

Google Search Console

The Core Web Vitals report identifies groups of URLs with good, needs-improvement, or poor performance on mobile and desktop. This helps website owners understand whether performance issues affect specific pages or wider sections of the website.

Chrome DevTools

For more detailed investigation, developers can use the Performance panel in Chrome DevTools. By recording an interaction, such as opening a menu or selecting a filter, they can examine whether the delay comes from JavaScript processing, other browser tasks, or rendering. Remember that Google's real-user Chrome UX data generally reflects a rolling 28-day period. Improvements made today may not immediately appear in field reports.

How to Improve INP Without Completely Redesigning Your Website

Improving website responsiveness doesn't always require rebuilding the entire website. In many cases, targeted technical changes can make a meaningful difference.

1. Identify the interactions causing delays

Start with the features visitors actually use. Test navigation menus, product filters, form submissions, search bars, and checkout buttons. Prioritise interactions that are both slow and important to your business.

2. Reduce unnecessary JavaScript work

Remove unused scripts, avoid running expensive operations during user interactions, and break lengthy processing tasks into smaller pieces where appropriate. This allows the browser more opportunities to respond to visitors.

3. Review third-party integrations

Check whether tracking scripts, chat tools, and other plugins are adding unnecessary processing work. Keep essential integrations, but optimize when and how they execute.

4. Make visual updates more efficient

Avoid unnecessary changes to large sections of a webpage when someone interacts with a single element. For actions involving additional processing, provide prompt visual feedback, such as a loading state, where appropriate.

5. Measure performance after making changes

Run the same interactions again, compare results, and monitor real-user data over time. Google's INP optimization guidance recommends identifying the source of interaction delays before deciding which changes to make. The goal is not simply to achieve a better score, but to make important website actions feel consistently responsive.

Conclusion

A website that loads quickly creates a good first impression. But what happens after that first impression is equally important. When buttons respond slowly, menus hesitate, or forms appear unresponsive, visitors experience a website that feels slower than its loading performance suggests. Google's Interaction to Next Paint (INP) metric helps businesses identify these hidden delays and understand how their websites respond during real interactions.

Rather than focusing exclusively on loading speed or perfect performance scores, businesses should pay attention to the complete browsing experience. At Wemonde, we believe website performance should support the way people actually use digital platforms. Identifying and improving slow interactions can help create websites that are not only quick to open but also easier and more reliable to use.