How can the "INP Issue- Longer than 200ms (Mobile) be resolved to enhance the website's performance and users' experiences?

The Interaction to Next Paint (INP) metric is pivotal in web performance analysis, particularly for mobile devices. INP measures the latency of the most extended single interaction—such as clicks, taps, or critical presses—when a user interacts with a webpage.

A higher INP score signifies noticeable delays, leading to a poor user experience.

Several steps must be undertaken to optimize your website's performance and enhance users' experiences. Here is a comprehensive step-by-step guide:

Measure and Identify

1. Use Performance Tools:

Utilize tools like Google Lighthouse, PageSpeed Insights, or WebPageTest to measure your INP score.

Run these tests specifically in mobile settings to obtain relevant data for mobile performance.

2. Analyze the Report:

Identify interactions taking longer than 200ms.

Look for specific elements or scripts causing delays.

Optimize JavaScript

1. Minimize JavaScript Execution Time:

Defer or asynchronously load JavaScript files that are not essential for the initial page load.

Split large JavaScript bundles into smaller chunks to load them as needed.

2. Optimize Event Handlers:

Avoid long-running event handlers. Break down complex logic into smaller, asynchronous tasks.

Use requestIdleCallback for non-critical operations that can wait until the browser is idle.

3. Remove Unused JavaScript:

Eliminate JavaScript from being used on the page to reduce the amount of code that needs to be processed.

Optimize CSS

1. Minimize CSS Blocking Time:

Ensure that CSS files are as small as possible and only contain necessary styles.

Use media queries to load CSS conditionally for specific devices.

Optimize Rendering Path

1. Reduce Layout Thrashing:

Avoid JavaScript, which forces layout recalculations and reflows. Batch DOM changes together to minimize reflows.

Use the will-change property in CSS to inform the browser about elements that will change, allowing for optimizations.

2. Improve Paint Performance:

Reduce the complexity of your page's layout and styling. Use more straightforward CSS rules and fewer elements.

Avoid large, complex CSS animations and transitions that can cause re-paints.

Optimize Images and Other Media

1. Optimize Image Sizes:

Use responsive images with appropriate sizes for mobile devices.

Compress images to reduce their file size without compromising quality.

2. Defer Offscreen Images:

Lazy load images that are not immediately visible on the screen to improve initial load performance.

Implement Service Workers and Caching

1. Use Service Workers:

Implement service workers to cache assets and improve the speed of subsequent page loads.

2. Optimize Caching Strategies:

Set appropriate cache headers for static assets to leverage browser caching.

Monitor and Iterate

1. Continuous Monitoring:

Regularly monitor your INP score using performance tools.

Set up automated performance testing as part of your CI/CD pipeline.

2. Iterative Optimization:

Continuously refine and optimize your codebase and assets based on monitoring data.

Additional Tips

• Reduce Third-Party Scripts: Limit the use of third-party scripts and services that can add latency.
• Preconnect and Prefetch: Use resource hints like <link rel= "preconnect"> and <link rel= "prefetch"> to optimize resource loading.
• Consider Using a CDN: A Content Delivery Network (CDN) can improve load times by serving assets from locations closer to your users.

Ideal INP Values

The ideal INP values, which ensure a good user experience, are as follows:

For Mobile:

Good: INP ≤ 200ms

Needs Improvement: 200ms < INP ≤ 500ms

Poor: INP > 500ms

For Desktop:

Good: INP ≤ 200ms

Needs Improvement: 200ms < INP ≤ 300ms

Poor: INP > 300ms

Interpretation

• Good: An INP of 200ms or less is considered optimal, indicating that the webpage responds quickly to user interactions and provides a smooth and responsive user experience.
• Needs Improvement: If the INP is between 200ms and 500ms for mobile or between 200ms and 300ms for desktop, the page's responsiveness is noticeable but not ideal. Users might start feeling slight delays.
• Poor: An INP greater than 500ms for mobile or greater than 300ms for desktop indicates significant delays in interaction responses, leading to a frustrating user experience.

Why These Values Matter

• User Expectations: Users expect near-instantaneous responses to their actions, especially on mobile devices where interactions are more frequent.
• Competitive Standards: High-performing websites maintain low INP values to keep users engaged and reduce bounce rates.
• Accessibility: Faster interactions improve accessibility, making it easier for users with disabilities to navigate and interact with web content.

Real-World Scenarios and Performance Impact

Scenario 1: E-commerce Site

Problem: A significant e-commerce site notices a high bounce rate during peak shopping seasons. Analysis reveals that interactions like adding items to the cart or checking out have INP values exceeding 500ms.

Impact: Slow interactions lead to user frustration, abandoned carts, and lost sales.

Solution: By deferring non-essential JavaScript and optimizing event handlers, the site reduces INP to under 200ms, resulting in smoother interactions and higher conversion rates.

Scenario 2: News Portal

Problem: A popular news portal experiences user complaints about slow navigation when opening articles or interacting with multimedia content. The INP values range between 300ms to 700ms.

Impact: Readers experience delays discouraging further engagement, reducing the average session duration.

Solution: By implementing lazy loading for images and deferring offscreen elements, the portal improves INP to around 150ms, enhancing user experience and increasing readership.

Scenario 3: Social Media Platform

Problem: A social media platform finds that interactions like liking posts or loading comments are sluggish, with INP values often above 400ms.

Impact: Users find the platform less responsive than competitors, leading to decreased user engagement and activity.

Solution: Optimizing CSS and minimizing render-blocking resources helps the platform achieve INP values below 200ms, making interactions snappier and more satisfying for users.

Steps to Achieve Ideal INP Values

To maintain or achieve these ideal INP values, follow these optimization steps:

1. Minimize JavaScript Execution Time:Defer non-critical JavaScript.Use asynchronous loading for scripts.Optimize the size and execution of JavaScript files.
2. Optimize Event Handlers:Keep event handler functions small and efficient.Break complex logic into smaller, non-blocking tasks.
3. Reduce Render-Blocking Resources:Minimize and defer CSS files.Inline critical CSS.
4. Optimize Images and Media:Use responsive images.Compress and lazy load images.
5. Improve Network Performance:Use a Content Delivery Network (CDN).Enable HTTP/2 or HTTP/3.
6. Use Browser Performance APIs:Leverage the PerformanceObserver API to monitor and analyze interaction timings.
7. Enhance Caching Strategies:Utilize service workers for caching.Set appropriate cache-control headers.
8. Monitor and Iterate:Regularly test performance using tools like Lighthouse, WebPageTest, and PageSpeed Insights.Continuously refine based on user feedback and performance data.

By targeting these ideal INP values and consistently optimizing your web pages, you can significantly enhance the user experience across mobile and desktop platforms. Adopting these practices meets user expectations and aligns with competitive standards, ensuring your website remains efficient, accessible, and engaging.