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.