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Understanding Network Speeds
- 5G: High-speed modern mobile networks (~100 Mbps). Excellent performance.
- 4G/LTE: Standard mobile network (~10 Mbps). Good for most content.
- 3G: Older/rural mobile networks (~1 Mbps). Struggles with large assets.
- Slow 2G: Very slow connections (~100 Kbps). Optimization critical.
Note: Real-world speeds vary based on signal strength, congestion, and location.
Performance Metrics Explained
TTFB (Time to First Byte): Time from request to first server response. Good: < 200ms
FCP (First Contentful Paint): Time until first content appears. Good: < 1.8s
LCP (Largest Contentful Paint): Time until largest element loads. Good: < 2.5s
These are Core Web Vitals that Google uses for search rankings.
Asset Size Guidelines
- HTML: < 50 KB (compressed)
- CSS: < 100 KB total (compressed)
- JavaScript: < 200 KB initial load (compressed)
- Images: < 500 KB total above-the-fold
- Fonts: < 100 KB total
- Total page weight: < 1 MB initial load
Quick Optimization Tips
- Compress and minify all assets (HTML, CSS, JS)
- Use WebP or AVIF for images (30-50% smaller than JPEG)
- Lazy load images below the fold
- Defer or async non-critical JavaScript
- Use a CDN to reduce latency
- Enable Gzip or Brotli compression
- Set proper cache headers
- Limit web fonts to 2-3 families
Performance Budgets
Performance budgets are limits you set to maintain fast load times:
- Maximum file sizes for each asset type
- Maximum number of HTTP requests
- Maximum load time targets
- Core Web Vitals thresholds
Enforce budgets in your build process to prevent performance regressions.