Improve website performance with CSS by reducing reflows, minimizing paints, and optimizing rendering speed for smoother UX.
CSS Performance & Rendering Optimization | Reduce Reflows & Paints
Performance is a critical part of modern web development.
Even beautifully designed CSS can hurt user experience if rendering is slow.
This lesson covers how to reduce reflows, repaints, and improve rendering speed
with practical examples and explanations.
Why CSS Performance Matters
Browsers render pages in layers:
DOM construction: parsing HTML Style calculation: matching selectors to elements Layout (reflow): calculating positions and sizes Paint: drawing pixels Composite: layering elements on screen Info!
Layout, paint, and composite steps are the heaviest operations.
Minimizing them improves FPS and reduces jank.
Reflows (Layout Thrashing)
A reflow happens whenever the browser recalculates layout.
Changing geometry, sizes, or positions triggers it.
Reflow Example (Expensive) ✏️ Edit ▶ Run <div class="container">
<div class="item">Item 1</div>
<div class="item">Item 2</div>
</div>
<style>
.container {
displa…
