HTML and CSS Animations
Animations
CSS animations run keyframe sequences directly in the browser, ideal for micro-interactions, loading indicators, and storytelling without heavy JavaScript.
Keyframe syntax
- Define an animation with
@keyframes name { ... }. - Specify property values at percentages (0%, 50%, 100%) or keywords (
from/to). - Apply the animation to elements with
animation-name,animation-duration, and related properties.
Note: Keyframes are snapshots of styles at certain times.
The browser fills in the frames between them automatically.
If you want to read more about CSS Animations or get an in-depth understanding, go to CSS Animations in our CSS tutorial.
Animation properties
animation-duration,animation-delaycontrol timing.animation-timing-functionsets easing between keyframes.animation-iteration-countdefines loop count orinfinite.animation-direction(normal,reverse,alternate).animation-fill-modedetermines styles before/after animation.
Note: animation-fill-mode: forwards keeps the final style after the animation finishes; backwards applies the first keyframe before it starts.
Use animation shorthand to set multiple values at once.
Example: Loading Pulse
This example defines a simple pulse using @keyframes and applies it to a dot.
The animation alternates between two states using the alternate direction.
Keyframes in action
<!DOCTYPE html>
<html>
<head>
<link rel="stylesheet" href="styles.css" type="text/css">
</head>
<body>
<div class="loader"></div>
</body>
</html>
.loader {
width: 16px;
height: 16px;
border-radius: 999px;
background: #2563eb;
animation: pulse 900ms ease-in-out infinite alternate;
}
@keyframes pulse {
from { transform: scale(0.75); opacity: 0.6; }
to { transform: scale(1.4); opacity: 1; }
}
The from/to keyframes scale and fade the dot.
The infinite alternate setting loops the animation back and forth smoothly.
Sequencing
- Use delays or staggered start times for list reveal animations.
- Combine multiple animations using comma-separated values.
- Paired elements can share keyframes with different durations or delays.
Accessibility considerations
- Respect
@media (prefers-reduced-motion: reduce): disable or simplify animations. - Avoid large parallax or flashing effects that cause motion sickness.
- Provide user controls for complex animated sequences.
Note: Always give users a way to pause long or looping animations so they do not become distracting.