🔥 CSS animation vs transition: Which 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 true?
• And does this hold for all CSS properties?

Let’s dive deeper.

🧪 Performance Testing at Scale

To get to the bottom of this, we built a stress-test environment with 7,500 animated elements and tracked a wide range of performance metrics:

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

👉 Try the live test yourself: click me

⚙️ How We Measured

To ensure objective and reliable results, our setup are:

• Renders thousands of elements on screen
• Waits briefly before starting animation or transition
• Captures performance metrics on every animation frame
• Repeats each test 50 times to collect median data

We tracked:

• 🎯 Average and lowest FPS
• ⏳ Frame delay and max spike
• 🧠 JavaScript memory usage
• 🔥 Peak memory during animation
• ⌛ Total duration of the effect

This method helps us understand how CSS animations behave under heavy load, not just in theory, but in actual browsers.

😱 What We Discovered

It might seem that modern browsers should handle thousands of animations effortlessly.

Spoiler: They don’t. Even 7,500 animated blocks cause visible frame drops and lag.

🧪 Test Case: opacity

Memory usage increased by 14.11% during animations compared to transitions, indicating higher resource consumption for animations.

Average FPS dropped to 12.04 with animations, which is 16.80% lower than with transitions. This shows that animations can cause more performance degradation under heavy load.

Transitions tend to use memory more efficiently due to simpler rendering and fewer internal calculations. Still, overall memory usage between the two remains comparable for small to moderate numbers of elements.

However, as the number of animated elements grows, animations increase memory consumption more steeply than transitions — a difference that becomes critical at high loads.

🤔 What About Other CSS Properties?

We also tested:

• transform (GPU-accelerated property)
• blur (expensive filter effect)
• background-color (paint-heavy property)

The results vary significantly depending on the property, browser, and hardware. For example, transform animations often perform better because they leverage GPU acceleration, while animating blur or background-color is more taxing on the CPU and memory.

👉 Try the test yourself and see how your browser handles these properties: Live test link.

💡 Additional Insights

• Transitions are often simpler: They represent a change from one state to another, which browsers can optimize more easily.
• Animations offer more control: Complex keyframe animations provide granular timing and sequences, but this complexity comes with a performance cost.
• Hardware acceleration matters: Animating properties like transform and opacity usually trigger GPU acceleration, which greatly improves smoothness and reduces CPU load.
• Avoid animating expensive properties: Properties like width, height, box-shadow, filter (especially blur) cause layout recalculations and repaints, which hurt performance.
• Batch animations: Group your animations and transitions where possible to reduce browser workload.

💬 Final Thoughts

Don’t assume one approach is always better. Performance depends on:

• The CSS property you’re animating
• The number of elements involved
• Browser optimizations and GPU usage

In general, transitions consume less memory and GPU than animations, especially at scale. But animations give you more control and flexibility, so it’s a trade-off.

We encourage you to experiment, profile, and push your browser to the limits to find the best approach for your specific case.

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