# Common performance pitfalls and how to avoid them — Web Performance Optimization

Source: https://www.geekswithgeeks.com/en/web-performance/web-perf-24

> Learn from common mistakes and anti-patterns that degrade performance.

## Performance anti-patterns

Avoid: unoptimized images, render-blocking CSS/JS, layout thrashing, polling instead of events, missing caching headers, bloated frameworks, inlining large resources, not testing on slow networks, ignoring third-party scripts. Each costs 100-1000ms of performance.

## Testing on realistic conditions

Always test on slow networks (3G, 4G), older devices (2-3 year old phones). DevTools throttling: Fast 3G = 1.6Mbps down, 750Kbps up, 40ms latency. Most real users aren't on fiber. Measure on real devices and networks regularly.

## Avoiding regressions

Set performance budgets in CI/CD. Use synthetic monitoring for early detection. Compare before/after metrics. Educate team on performance impact. Measure third-party impact (analytics, ads, tracking). Budget for unavoidable dependencies.

Quick check

**Quiz:** What is a common performance anti-pattern?

- [ ] Polling instead of events
- [ ] Using Service Workers
- [ ] Optimizing images