Performance Testing for Image Optimization

Learn how to effectively measure and test your image optimization efforts. Master the tools and metrics that matter for image performance.

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Key Performance Metrics

Largest Contentful Paint (LCP)
First Contentful Paint (FCP)
Cumulative Layout Shift (CLS)
Time to Interactive (TTI)
Total Blocking Time (TBT)

Performance Goals

LCP under 2.5 seconds
FCP under 1.8 seconds
CLS under 0.1
TTI under 3.8 seconds

Testing Tools

1. Browser Developer Tools

Network panel analysis
Performance timeline
Memory usage tracking
Lighthouse audits

Lighthouse Example

// Example Lighthouse CLI command
lighthouse https://example.com --only-categories=performance \
          --output=html --output-path=./report.html

Testing Best Practices

Test across different devices
Simulate various network conditions
Monitor real user metrics (RUM)
Compare before and after optimization
Document performance improvements

Testing Checklist

Baseline performance measurement
Optimization implementation
Post-optimization testing
Results documentation