Interaction to Next Paint (INP) Needs Improvement

Description

The page's Interaction to Next Paint (INP) score needs improvement, which may affect user experience.

How to Fix

Optimize JavaScript execution, reduce main thread work, and minimize layout shifts during interactions. Consider code-splitting and optimizing event handlers.

Detailed Analysis

1. What causes the issue:

Interaction to Next Paint (INP) is a web performance metric that measures the time from when a user interacts with a page (such as clicking a button) until the next frame is painted. An INP score that needs improvement typically indicates delays in how quickly a page responds to user interactions. Several factors can contribute to an unsatisfactory INP score:

• Heavy JavaScript Execution: Large or poorly optimized JavaScript files can block the main thread, delaying subsequent user interactions.
• Long Task Duration: If tasks on the main thread take too long to execute, they can prevent the browser from being responsive to user inputs.
• Inefficient Rendering: Complex CSS or layout thrashing can cause additional rendering work that delays painting.
• Network Latency: Delays in fetching critical resources, such as stylesheets and scripts, can indirectly affect INP by delaying the execution of necessary scripts.
• Poor Resource Prioritization: If resources required for interactive elements are loaded late, this can delay the interaction response.

2. Why it's important:

The INP is crucial because it directly impacts user experience. Slow interactions can lead to frustration and increased bounce rates, as users expect instantaneous responses when they interact with a webpage. This metric is particularly important in today’s digital environment where user expectations for speed are higher than ever. Improving INP can lead to:

• Enhanced User Satisfaction: Faster interactions create a smoother and more enjoyable user experience.
• Better Engagement: Responsive pages can increase the time users spend on site and their likelihood of interacting with content.
• Improved SEO Performance: Google considers user experience metrics like INP when ranking pages, so improving it can potentially lead to higher search rankings.

3. Best practices to prevent it:

• Optimize JavaScript: Minimize and defer the loading of non-essential JavaScript. Use code-splitting to ensure only necessary code is loaded initially.
• Reduce Long Tasks: Break up long tasks into smaller asynchronous ones to prevent blocking the main thread.
• Efficiently Manage Rendering: Avoid layout thrashing by minimizing changes to the DOM and using CSS efficiently. Use the transform and opacity properties for animations to avoid triggering layout changes.
• Use Web Workers: Offload heavy computations to web workers to keep the main thread free for user interactions.
• Prioritize Critical Resources: Load critical CSS and JavaScript as early as possible and defer non-critical resources.
• Monitor and Test Performance: Regularly use tools like Lighthouse or WebPageTest to identify and address performance bottlenecks.

4. Examples of good and bad cases:

• Bad Case Example:

  • A website with heavy reliance on large JavaScript libraries that are loaded synchronously, causing a delay before the page becomes interactive. Users click on buttons, but there is a noticeable lag before any response occurs, leading to a poor INP score.

• Good Case Example:

  • A web page that loads content progressively, using lazy-loading for images and deferring non-essential scripts. The site uses async and defer attributes for script tags, ensuring that the main content is interactive quickly. User interactions, such as button clicks, are processed immediately, resulting in a swift response and a good INP score.

Improving INP involves a strategic approach to resource loading, execution prioritization, and efficient rendering practices, all aimed at creating a seamless user experience.