What is Web Performance?
Web performance refers to how quickly web pages load and become interactive in a user's browser. It encompasses multiple aspects including server response time, asset download speed, rendering performance, and perceived load time.
Key Metrics
The most important web performance metrics include Largest Contentful Paint (LCP), which measures loading performance. A good LCP score is under 2.5 seconds. First Input Delay (FID) measures interactivity, with good scores under 100 milliseconds. Cumulative Layout Shift (CLS) measures visual stability, with good scores under 0.1.
Common Performance Bottlenecks
Large unoptimized images are the most common cause of slow page loads. Render-blocking JavaScript and CSS prevent the browser from displaying content until they've fully loaded. Too many HTTP requests from excessive third-party scripts slow down every page load. Server-side rendering issues like slow database queries or uncached API responses increase Time to First Byte.
Optimization Strategies
Image optimization through compression, modern formats like WebP, and lazy loading can dramatically reduce page weight. Code splitting ensures users only download the JavaScript they need for the current page. Browser caching with proper cache headers reduces repeat visit load times. Content delivery networks distribute assets geographically closer to users.