Web Performance Basics Every Developer Should Know
Performance Development

Web Performance Basics Every Developer Should Know

Web performance isn't just a nice-to-have. Studies consistently show that faster sites have better engagement, lower bounce rates, and higher conversion rates. Google also uses page speed as a ranking factor.

Core Web Vitals

Google's Core Web Vitals are the metrics that matter most:

Largest Contentful Paint (LCP)

Measures loading performance. Aim for LCP within 2.5 seconds of page load.

How to improve:

  • Optimize and compress images
  • Use a CDN
  • Preload critical resources
  • Remove render-blocking JavaScript

First Input Delay (FID) / Interaction to Next Paint (INP)

Measures interactivity. Users should be able to interact within 100ms.

How to improve:

  • Break up long JavaScript tasks
  • Use web workers for heavy computation
  • Defer non-critical JavaScript
  • Minimize main thread work

Cumulative Layout Shift (CLS)

Measures visual stability. Keep CLS under 0.1.

How to improve:

  • Always include size attributes on images
  • Reserve space for ads and embeds
  • Avoid inserting content above existing content
  • Use CSS transforms for animations

Quick Wins

1. Optimize Images

Images are often the biggest performance culprit. Use:

  • Modern formats (WebP, AVIF)
  • Responsive images with srcset
  • Lazy loading for below-fold images
  • Proper compression

2. Minimize JavaScript

Every byte of JavaScript costs more than other resources because it must be parsed, compiled, and executed.

  • Audit and remove unused code
  • Code-split by route
  • Defer non-critical scripts
  • Consider if you really need that library

3. Leverage Browser Caching

Set appropriate cache headers so returning visitors don't re-download static assets.

4. Use a CDN

Content Delivery Networks serve assets from locations closer to your users, dramatically reducing latency.

Measuring Performance

You can't improve what you don't measure. Use these tools:

  • Lighthouse: Built into Chrome DevTools
  • PageSpeed Insights: Google's public tool
  • WebPageTest: Detailed waterfall analysis
  • Real User Monitoring (RUM): Track actual user experience

Performance is a Feature

Building performant websites isn't extra work - it's part of building quality software. Start with performance in mind, and you'll save yourself from painful optimization later.

Need help optimizing your site? Contact us for a performance audit.