Performance Tests

This suite compares the performance characteristics of CSS Modules and Styled Components in React applications. Each test runs identical scenarios using both styling approaches to help you make informed decisions about styling solutions.

Note that results can vary between runs due to system load, browser state, and other environmental factors. These results represent general performance trends rather than absolute measurements.

1. Initial Load Performance

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Measures how quickly a page loads and renders its initial content. Compares first-paint performance and setup overhead between CSS Modules and Styled Components.

2. Hydration Performance

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Tests how fast the application becomes interactive after server-side rendering. Compares hydration performance between CSS Modules and Styled Components.

3. Change CSS Prop Tests

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Measures performance when frequently updating individual CSS properties. Compares both approaches for animations and interactive UI elements.

4. Change Variant Tests

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Tests how quickly styles can be switched between different variants. Compares both approaches for theme switching and state-based styling.

5. Create and Mount Tests

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Measures the overhead of creating and mounting new styled elements. Compares both approaches for dynamically generated UIs.

6. Mount Deep Tree Tests

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Tests performance with deeply nested components. Compares both approaches for complex layouts and component hierarchies.

7. Mount Wide Tree Tests

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Measures performance with many sibling components. Compares both approaches for rendering large lists, grids, and data-heavy UIs.

Summary of Results

Based on the performance tests above, CSS Modules consistently outperformed Styled Components across all metrics:

  • Initial Load: CSS Modules approach was 41% faster (1.33ms vs 2.25ms)
  • Hydration: CSS Modules approach was 31% faster (0.43ms vs 0.62ms)
  • Change CSS Prop: CSS Modules approach was 86% faster (0.006ms vs 0.042ms)
  • Change Variant: CSS Modules approach was 91% faster (0.003ms vs 0.032ms)
  • Create and Mount: CSS Modules approach was 97% faster (0.005ms vs 0.15ms)
  • Mount Deep Tree: CSS Modules approach was 45% faster (2.4ms vs 4.38ms)
  • Mount Wide Tree: CSS Modules approach was 47% faster (3.27ms vs 6.16ms)