Poor Interaction to Next Paint (INP) Score

Description

The page has a poor Interaction to Next Paint (INP) score, signaling slow interactivity.

How to Fix

Prioritize optimizing JavaScript execution, reduce third-party script impact, implement efficient event delegation, and minimize layout shifts during interactions.

Detailed Analysis

Interaction to Next Paint (INP) is a metric used to assess the responsiveness of a web page. It measures the time taken for the next paint after a user interacts with the page, such as clicking a button or entering text. A poor INP score indicates that users experience delays in feedback from the website after interactions, leading to a perception of sluggishness and reducing overall user satisfaction.

1. What Causes This Issue

Several factors can contribute to a poor INP score, including:

• JavaScript Execution: Heavy or inefficient JavaScript can block the main thread, delaying the response to user interactions.
• Resource Load Time: Large or unoptimized resources (images, scripts, styles) can delay the execution of interactions as they compete for network bandwidth.
• Render-Blocking Resources: CSS and scripts that block rendering can delay the time to interactive, causing slower response times.
• Main Thread Bottleneck: Tasks that take place on the main thread, such as layout calculations or style recalculations, can delay interaction processing.
• Long Tasks: Tasks taking more than 50 milliseconds can lead to delayed user feedback and subsequently poor INP.

2. Why It's Important

• User Experience: A poor INP score leads to sluggish feedback after user interactions, which can frustrate users, reduce satisfaction, and lead to higher bounce rates.
• SEO Performance: Search engines, especially Google, prioritize user experience. A poor INP score can negatively affect your Core Web Vitals, impacting your search rankings.
• Conversion Rates: Delays in interactivity can lead to lost opportunities for conversions, as users may abandon slow sites.

3. Best Practices to Prevent It

• Optimize JavaScript: Minimize and defer non-critical JavaScript. Use code-splitting and lazy loading for scripts that aren't needed immediately.
• Efficient Resource Loading: Use modern image formats like WebP, optimize images, and ensure scripts/styles are minified and compressed.
• Defer Render-Blocking Resources: Prioritize critical rendering paths and defer or asynchronously load CSS and JavaScript that aren't necessary for initial page load.
• Reduce Long Tasks: Break up long-running tasks into smaller, asynchronous chunks to keep the main thread responsive.
• Use Web Workers: Offload heavy computations to web workers, which run in the background and don't block the main thread.
• Preload Important Assets: Preload fonts and critical resources to ensure they're available as soon as needed.

4. Examples of Good and Bad Cases

Good Case:

• Site A has optimized scripts and images, defers non-critical resources, and uses web workers to handle intensive tasks. As a result, when a user clicks a button, the next paint is almost instantaneous, providing a smooth user experience.

Bad Case:

• Site B loads large JavaScript files on the main thread and uses render-blocking CSS. When a user attempts to interact, the site lags significantly, and the feedback from the interaction is delayed, resulting in a poor INP score and frustrated users.

By addressing the factors contributing to poor INP scores, web developers can significantly enhance the interactivity and responsiveness of their websites, leading to better user experiences, improved SEO performance, and higher conversion rates.