Optimizing Web Performance
Techniques and tools for building blazing-fast websites that users and search engines love.
Web performance is not a luxury; it is a competitive advantage that directly impacts user engagement, conversion rates, and search engine rankings. Google’s Core Web Vitals are now a ranking factor, and studies consistently show that even a 100-millisecond delay in page load time can reduce conversions by several percent. Here are the techniques that deliver the greatest performance improvements for the least implementation effort.
Images: The Low-Hanging Fruit
Images typically account for fifty to seventy percent of a page’s total weight. Serving them in modern formats like AVIF and WebP with JPEG fallbacks can reduce file sizes by forty to sixty percent without visible quality loss. Use the HTML picture element to serve the optimal format based on browser support, and implement responsive images with srcset to deliver appropriately sized versions for each viewport.
Lazy loading defers the download of off-screen images until the user scrolls near them, dramatically improving initial page load time. The native loading=“lazy” attribute requires no JavaScript and is supported by all modern browsers. For critical above-the-fold images, use loading=“eager” and add fetchpriority=“high” to ensure they load as quickly as possible.
JavaScript Optimization
Audit your JavaScript bundles regularly using tools like Webpack Bundle Analyzer or Vite’s built-in visualizer. Third-party scripts for analytics, chat widgets, and social embeds often account for a surprising portion of total JavaScript weight. Load non-essential scripts asynchronously and defer them until after the main content has rendered.
Code splitting ensures that users download only the JavaScript needed for the current page. Modern bundlers like Vite and Next.js implement code splitting automatically at the route level, but you can further optimize by dynamically importing heavy components that are only visible after user interaction, such as modals, complex charts, or rich text editors.
Critical Rendering Path
The critical rendering path determines how quickly the browser can render the initial view of your page. Inline critical CSS, the minimum styles needed to render above-the-fold content, directly in the HTML head, and load the remaining stylesheet asynchronously. This technique eliminates the render-blocking behavior of external CSS files and can cut First Contentful Paint by several hundred milliseconds.
Preconnect to third-party origins that your page will need, such as font providers, CDNs, and API servers. The preconnect hint establishes the TCP connection and TLS handshake before the resource is actually requested, saving 100 to 300 milliseconds per origin on subsequent requests.
Caching and CDN Strategy
Implement aggressive caching headers for static assets. Files with content hashes in their names can safely use cache-control max-age values of one year, since the filename changes whenever the content changes. For HTML documents, use shorter cache durations or stale-while-revalidate strategies that serve cached content while fetching updates in the background.
A Content Delivery Network places copies of your assets on servers distributed worldwide, ensuring that users download files from the geographically nearest location. Modern CDNs like Cloudflare, Vercel Edge, and AWS CloudFront also offer edge computing capabilities that can server-render pages at the CDN edge, combining the performance of static files with the flexibility of dynamic content.