🔥 CSS animation vs transition: Which one performs better?

Every front-end developer has faced this dilemma at least once:

Should you use animation or transition?

The common wisdom says transition is faster—but is that really true?

And does that apply to all CSS properties?

Let’s find out.

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🧪 Performance testing at scale

To uncover the truth, we built a stress-test environment with 2,500+ animated elements and tracked a wide range of performance metrics:

• ✅ Average and lowest FPS
• ⏱️ Frame delay (delta) and max spike
• 💾 JavaScript heap usage
• 📈 Peak memory consumption
• 🧮 Total allocated memory
• 🕐 Total task duration

📊 The most telling metric?

How long does it take for the animation to complete fully — that’s our benchmark.

👉 Try the live test environment

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⚙️ How we measured

To ensure objective results, our setup:

• Renders thousands of elements on the screen
• Waits briefly before starting the animation/transition
• Captures performance metrics on every animation frame

What we tracked:

• 🎯 Average & lowest FPS
• ⏳ Frame delay (delta) and its peak
• 🧠 JavaScript memory usage
• 🔥 Peak memory during animation
• ⌛ Full duration of the animation

This helped us understand how CSS animations behave under load—not just in theory, but in real browsers.

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😱 What we found

You might think modern browsers can handle thousands of animations.

Spoiler: They can’t.

Just ~2,000 animated blocks are enough to cause visible frame drops and lag.

Here’s a snapshot of the test: hundreds of blocks animating in the background, while performance metrics are tracked live in the center of the screen.

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🧪 Test Case: opacity

One of our simplest test cases was the opacity property.

• With animation → 15.91s
• With transition → 16.13s

Surprised? We were, too.

Transitions were slightly slower in this case—challenging the assumption that they’re always more performant.

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🤔 What about other css-properties?

We also tested:

• transform
• blur
• background-color

But we won’t spoil those results 😉

👉 Try the test yourself and see how your browser handles them.

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💬 Final thoughts

Don’t assume one approach is always better.

Performance can vary depending on:

• The CSS property you're animating
• The number of elements involved
• How the browser optimizes each case

We invite you to experiment, analyze, and maybe even break your browser in the process 😄

If you found this useful — leave a ❤️ or 🦄 so others can discover it too!