Using Web Vitals to Guide Improvements

Introduction

Web Vitals are a set of metrics that help developers understand the user experience of their web applications. They are especially important for Progressive Web Apps (PWAs) as they ensure a fast, responsive, and engaging user experience. This lesson will guide you on how to use Web Vitals to improve your PWA.

What are Web Vitals?

Web Vitals are essential metrics that reflect the quality of a user's experience on the web. Key Web Vitals metrics include:

• Largest Contentful Paint (LCP)
• First Input Delay (FID)
• Cumulative Layout Shift (CLS)

Key Web Vitals Metrics

1. Largest Contentful Paint (LCP)

LCP measures loading performance. It marks the point in the page load timeline when the largest text block or image is rendered.

2. First Input Delay (FID)

FID measures interactivity. It quantifies the time it takes for a user to interact with the page after it first loads.

3. Cumulative Layout Shift (CLS)

CLS measures visual stability. It quantifies how much the page layout shifts during its lifecycle.

Implementing Web Vitals

Implementing Web Vitals can be done using the Web Vitals library. Here’s how to set it up:

        <script src="https://unpkg.com/web-vitals/dist/web-vitals.iife.js"></script>
        <script>
            function sendToAnalytics(metric) {
                const body = JSON.stringify(metric);
                navigator.sendBeacon('/analytics', body);
            }
            webVitals.getLCP(sendToAnalytics);
            webVitals.getFID(sendToAnalytics);
            webVitals.getCLS(sendToAnalytics);
        </script>
        

Best Practices

To improve Web Vitals in your PWA, consider the following best practices:

1. Optimize images and videos for faster loading.
2. Minimize JavaScript and CSS blocking time.
3. Implement lazy loading for images and iframes.
4. Utilize a content delivery network (CDN) for faster content delivery.

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