Core Web Vitals in 2024: What Changed and How to Adapt

Google's Core Web Vitals continue to evolve, and 2024 brought significant changes that affect how we measure and optimize web performance. Let's dive into what's new and how to adapt.

INP Replaces FID

The biggest change is Interaction to Next Paint (INP) replacing First Input Delay (FID) as a Core Web Vital.

Why the Change?

FID only measured the first interaction, while INP measures all interactions throughout the page lifecycle. This provides a more complete picture of responsiveness.

INP Thresholds

• **Good**: ≤200ms
• **Needs Improvement**: 200-500ms
• **Poor**: >500ms

Optimizing for INP

Here are practical strategies to improve your INP scores:

1. Break Up Long Tasks

Long JavaScript tasks block the main thread. Break them into smaller chunks:

// Instead of one long task
function processItems(items) {
  for (const item of items) {
    // Using scheduler.yield() or setTimeout
    await scheduler.yield();
    processItem(item);
  }
}

2. Optimize Event Handlers

Keep event handlers fast and defer non-essential work:

button.addEventListener('click', () => {
  // Visual feedback immediately
  button.classList.add('clicked');

  // Defer heavy work
  requestIdleCallback(() => {
    performHeavyOperation();
  });
});

3. Use CSS Containment

CSS containment limits browser calculations:

.card {
  contain: layout style paint;
}

LCP Optimization Remains Critical

Largest Contentful Paint (LCP) is still crucial. Key strategies:

• Preload hero images
• Use responsive images with proper sizing
• Implement priority hints
• Optimize server response time

Tools for Measurement

Use these tools to measure your Core Web Vitals:

1. **PageSpeed Insights** - Lab and field data
2. **Chrome DevTools** - Performance panel
3. **Search Console** - Real user metrics
4. **Web Vitals Extension** - Quick checks

Conclusion

The shift to INP reflects how users actually experience websites. Focus on keeping interactions responsive throughout the entire page lifecycle, not just the first click.