Building Performant Web Applications

Performance is crucial for user experience and SEO. In this post, we’ll explore key principles for building fast web applications.

Core Performance Principles

1. Minimize Critical Resources

Critical rendering path includes resources needed for initial render:

• HTML document
• Critical CSS
• Essential JavaScript

Optimize by:

• Inlining critical CSS
• Deferring non-critical JavaScript
• Preloading important fonts

2. Use Efficient Images

Images often account for most page weight:

• Use modern formats (WebP, AVIF)
• Implement lazy loading
• Serve responsive images with srcset
• Compress without quality loss

3. Code Splitting

Split code into smaller chunks:

• Route-based splitting
• Component-level splitting
• Dynamic imports for heavy features

4. Optimize JavaScript

Reduce JavaScript bundle size:

• Tree-shaking to remove unused code
• Minification
• Avoid large dependencies
• Use lighter alternatives

Measurement Tools

Use these tools to measure performance:

• Lighthouse: Integrated in Chrome DevTools
• WebPageTest: Detailed performance metrics
• PageSpeed Insights: Core Web Vitals
• Chrome DevTools: Real-time analysis

Core Web Vitals

Google’s Core Web Vitals:

• LCP: Largest Contentful Paint (< 2.5s)
• FID: First Input Delay (< 100ms)
• CLS: Cumulative Layout Shift (< 0.1)

Continuous Optimization

Performance is not one-time task:

• Set up performance budgets
• Monitor in production
• Regularly audit
• Stay updated with best practices

Conclusion

Building performant web apps requires attention to detail and continuous improvement. Focus on user experience and measure results objectively.

Start with the basics and iterate. Small improvements compound into significant gains.