web-performance-optimization

Web Performance Optimization - Improve Website Loading Speed and User Experience

Skill Overview

Help developers systematically optimize website and web application performance by measuring and analyzing issues, diagnosing bottlenecks, implementing optimizations, and validating results—improving load speed, enhancing Core Web Vitals metrics, and strengthening user experience and SEO rankings.

Use Cases

1. Slow Website Loading

When users report that the site takes too long to open and bounce rates are high, use Lighthouse audits and performance analysis to locate bottlenecks and perform systematic improvements targeting issues such as JavaScript bundle size, image resources, and server response time.

2. Core Web Vitals Not Meeting Targets

When metrics such as LCP (Largest Contentful Paint), FID (First Input Delay), and CLS (Cumulative Layout Shift) fall short, provide tailored optimization plans to help improve Google search rankings.

3. Oversized Resource Bundles

When JavaScript or CSS bundle size impacts loading performance, reduce bundle size using techniques such as code splitting, on-demand loading, and removing unused dependencies to improve Time to Interactive (TTI).

Core Features

1. Performance Measurement and Diagnosis

Use tools such as Lighthouse and Chrome DevTools to establish performance baselines, analyze Core Web Vitals metrics, identify bottlenecks such as large files, render-blocking resources, and long tasks, and provide data-driven support for optimization.

2. Resource Optimization Implementation

Optimize resources including images, JavaScript, and CSS by converting to modern image formats (WebP, AVIF), implementing code splitting, adding lazy loading, configuring caching strategies, and optimizing the critical rendering path.

3. Validation and Monitoring

Compare Lighthouse scores and Core Web Vitals metrics before and after optimization to verify improvements, establish continuous monitoring, and ensure performance gains remain stable long term.

Common Questions

Where should I start if my website is too slow?

Start by running a Lighthouse audit to establish a performance baseline, focusing on three key metrics: LCP (should be within 2.5 seconds), FID (should be within 100 milliseconds), and CLS (should be less than 0.1). Typically, begin with high-impact optimizations such as reducing image sizes, decreasing JavaScript bundle size, and implementing code splitting.

What do LCP, FID, and CLS mean individually? How can I optimize them?

LCP (Largest Contentful Paint): Measures how quickly the page’s main content loads. Improve it by preloading critical resources, optimizing above-the-fold images, and using a CDN.

FID (First Input Delay): Measures how quickly the page responds to user interaction. Optimize by reducing JavaScript execution time and using code splitting.

CLS (Cumulative Layout Shift): Measures visual stability. Ensure space is reserved for images and dynamic content to prevent layout shifts.

How can I effectively reduce JavaScript bundle size?

Use webpack-bundle-analyzer to analyze bundle composition, remove unused dependencies, replace heavy libraries with lighter alternatives (e.g., use date-fns instead of moment.js), implement route-level and component-level code splitting, and defer non-critical functionality until after page interaction to load it.