What is the difference between CSS animations and CSS transitions?

CSS transitions animate between two states when a property changes, like on hover or focus. CSS animations use @keyframes to define multi-step sequences that can run automatically on page load, loop indefinitely, or play in reverse. Use transitions for simple state changes and animations for complex, multi-stage effects.

How do I make a CSS animation run only once when the page loads?

Set the animation on the element's default state (not a pseudo-class like :hover), use animation-iteration-count: 1, and omit animation-delay or set it to 0s. The animation will play immediately on render and stop after one cycle.

Can CSS animations affect page performance?

Animations that change properties like width, height, top, or left trigger layout recalculations on every frame, which can cause jank on slower devices. Stick to transform and opacity for smooth 60fps performance—browsers can optimize these via GPU compositing.

How do I pause a CSS animation on hover?

Use animation-play-state: paused inside a :hover rule. The animation will freeze at its current frame when the user hovers and resume when they move the mouse away. This is useful for carousel controls and interactive timelines.

Do CSS animations work on mobile browsers in 2026?

Yes. All mobile browsers since 2017 support unprefixed CSS animations. The builder outputs modern syntax without -webkit- or -moz- prefixes, which are no longer needed.

How do I sync multiple CSS animations to start at the same time?

Apply the same animation-name and animation-duration to all target elements. If they share the same animation-delay (or none), they will start in sync. For staggered timing, increment the delay value across elements using nth-child selectors or inline styles.

CSS Animation Keyframe Builder

This tool builds CSS keyframe animations using a visual timeline editor. Define your keyframe stops, set the animated CSS properties and values at each stop, choose your timing function and duration, and the tool outputs the complete @keyframes block and animation shorthand property. Everything runs in your browser. Your animation configurations never leave your device.

How does the CSS Animation Keyframe Builder work step by step?

CSS animations require two parts: a @keyframes declaration that defines the animation stages, and animation properties that control playback. The @keyframes rule names your animation and sets CSS properties at specific percentages of the animation timeline. For example, a fade-in effect might set opacity: 0 at 0% and opacity: 1 at 100%.

What does a typical CSS Animation Keyframe Builder result look like?

You want a button that pulses gently to draw attention, scaling up slightly and brightening. Keyframes: - 0%: transform: scale(1); box-shadow: 0 0 0 0 rgba(26,35,126,0.4); - 70%: transform: scale(1.05); box-shadow: 0 0 0 10px rgba(26,35,126,0); - 100%: transform: scale(1); box-shadow: 0 0 0 0 rgba(26,35,126,0);

Frequently asked questions

What is the difference between CSS animations and CSS transitions?
CSS transitions animate between two states when a property changes, like on hover or focus. CSS animations use @keyframes to define multi-step sequences that can run automatically on page load, loop indefinitely, or play in reverse. Use transitions for simple state changes and animations for complex, multi-stage effects.
How do I make a CSS animation run only once when the page loads?
Set the animation on the element's default state (not a pseudo-class like :hover), use animation-iteration-count: 1, and omit animation-delay or set it to 0s. The animation will play immediately on render and stop after one cycle.
Can CSS animations affect page performance?
Animations that change properties like width, height, top, or left trigger layout recalculations on every frame, which can cause jank on slower devices. Stick to transform and opacity for smooth 60fps performance—browsers can optimize these via GPU compositing.
How do I pause a CSS animation on hover?
Use animation-play-state: paused inside a :hover rule. The animation will freeze at its current frame when the user hovers and resume when they move the mouse away. This is useful for carousel controls and interactive timelines.
Do CSS animations work on mobile browsers in 2026?
Yes. All mobile browsers since 2017 support unprefixed CSS animations. The builder outputs modern syntax without -webkit- or -moz- prefixes, which are no longer needed.
How do I sync multiple CSS animations to start at the same time?
Apply the same animation-name and animation-duration to all target elements. If they share the same animation-delay (or none), they will start in sync. For staggered timing, increment the delay value across elements using nth-child selectors or inline styles.