In Web development, performance is not just a technical metric; it's the core of user experience. Google research shows that every 1-second delay in page load time causes a 20% drop in conversion rates. This article shares practical Web performance optimization experiences from real projects.
Key Performance Indicators (Core Web Vitals)
Before optimizing, we need to know the standards. Google's Core Web Vitals are currently the authoritative metrics:
- LCP (Largest Contentful Paint): Measures loading speed. Goal: < 2.5s.
- INP (Interaction to Next Paint): Measures responsiveness. Goal: < 200ms.
- CLS (Cumulative Layout Shift): Measures visual stability. Goal: < 0.1.
Practical Optimization Strategies
1. Image Optimization
Images are usually the largest resources on a page.
- Use Modern Formats: WebP or AVIF formats are typically over 30% smaller than JPEG/PNG.
- Lazy Loading: Add `loading="lazy"` attribute to images not visible on the first screen.
- Responsive Images: Use `srcset` to load different sized images based on screen size.
2. Resource Compression & Bundling
Reducing HTTP requests and resource size is key to performance.
- Gzip/Brotli Compression: Ensure the server enables compression for text resources.
- Code Splitting: Don't bundle all JS into one huge file; load on demand.
3. Leverage Browser Caching
Reasonable caching strategies allow returning visitors to load pages instantly. For static resources (JS, CSS, Images), set a long `Cache-Control: max-age=31536000`, combined with filename hashing (e.g., `main.a1b2c3.js`) to handle updates.
4. Reduce JavaScript Execution
JS is the main thread killer. Excessive JS blocks rendering, causing page lag.
- Remove unused code (Tree Shaking).
- Defer non-critical JS (`defer` or `async`).
- Use Web Workers to move heavy calculations off the main thread.
Recommended Tools
Good tools are essential for good work.
- Lighthouse: Chrome's built-in performance scoring tool, providing specific optimization suggestions.
- WebPageTest: Provides detailed loading waterfalls and multi-location testing.
- Image Toolbox: Our own online tool for convenient image compression and format conversion.
Conclusion
Performance optimization is an ongoing process, not a one-time task. As browser technologies evolve, optimization methods update constantly. Stay tuned and test regularly to keep your website in top shape.