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The animation property is used to call and control an @keyframe animation. Like this:

.element-to-animate {
  animation: NAME-YOUR-ANIMATION 5s infinite;
}

Which refers to a keyframe like this:

@keyframes NAME-YOUR-ANIMATION {
  0%   { opacity: 0; }
  100% { opacity: 1; }
}

You’ll need vendor prefixes to get good browser support:

@-webkit-keyframes NAME-YOUR-ANIMATION {
  0%   { opacity: 0; }
  100% { opacity: 1; }
}
@-moz-keyframes NAME-YOUR-ANIMATION {
  0%   { opacity: 0; }
  100% { opacity: 1; }
}
@-o-keyframes NAME-YOUR-ANIMATION {
  0%   { opacity: 0; }
  100% { opacity: 1; }
}
@keyframes NAME-YOUR-ANIMATION {
  0%   { opacity: 0; }
  100% { opacity: 1; }
}
#box {
  -webkit-animation: NAME-YOUR-ANIMATION 5s infinite;
  -moz-animation:    NAME-YOUR-ANIMATION 5s infinite;
  -o-animation:      NAME-YOUR-ANIMATION 5s infinite;
  animation:         NAME-YOUR-ANIMATION 5s infinite;
}

At the time of this writing the three vendor prefixes used above are the only ones implemented. At this point it’s likely that the non-prefixed version will start to get implemented soon without major changes, so you may want to consider using non-prefixed versions as well.

For the sake of brevity the rest of the code on this page will omit prefixes, but real world usage should use all the vendor prefixes.

Multiple steps

@keyframes fontbulger {
  0% {
    font-size: 10px;
  }
  30% {
    font-size: 15px;
  }
  100% {
    font-size: 12px;
  }
}

#box {
  animation: fontbulger 2s infinite;
}

If an animation has the same starting and ending properties, one way to do that is to comma-separate the 0% and 100% values:

@keyframes fontbulger {
  0%, 100% {
    font-size: 10px;
  }
  50% {
    font-size: 12px;
  }
}

Or, you could always tell the animation to run twice (or any even number of times) and tell the direction to alternate.

Calling keyframe animation with separate properties

#box {
  animation-name: bounce;
  animation-duration: 4s;
  animation-iteration-count: 10;
  animation-direction: alternate;
  animation-timing-function: ease-out;
  animation-fill-mode: forwards;
  animation-delay: 2s;
}
timing-function ease, ease-out, ease-in, ease-in-out, linear, cubic-bezier(x1, y1, x2, y2) (e.g. cubic-bezier(0.5, 0.2, 0.3, 1.0))
duration & delay Xs or Xms
duration-count X
fill-mode forwards, backwards, both, none
animation-direction normal, alternate

Animation Shorthand

Just space-separate all the individual values. The order doesn’t matter except when using both duration and delay, they need to be in that order. In the example below 1s = duration, 2s = delay, 3 = iterations.

animation: test 1s 2s 3 alternate backwards

Combine transform and animation

@keyframes infinite-spinning {
  from {
    transform: rotate(0deg);
  }
  to {
    transform: rotate(360deg);
  }
}

Multiple animations

You can comma-separate the values to declare multiple animations on a selector.

.animate-this {
   animation: 
     first-animation 2s infinite, 
     another-animation 1s;
}

Browser Support

Chrome Safari Firefox Opera IE Android iOS
6+ 5+ 5+ 12+ 10+ TBD 4+