The animation-timing-function property in CSS3 is a crucial player in dictating the flow of animations. It determines how intermediate property keyframes are calculated between the start and end of an animation sequence.

Simply put, animation-timing-function controls the speed curve of an animation. It defines how quickly or slowly an animation progresses at different points within its duration. This property allows you to create more realistic, non-linear motion for animated elements.

Consider an animation of a ball falling under gravity. It doesn’t fall at a constant speed; instead, it accelerates over time due to gravity. The animation-timing-function property allows you to simulate this acceleration.

Let’s demonstrate this with a simple example:

@keyframes bounce {
  0% {
    top: 0;

  100% {
    top: 200px;

.ball {
  animation-name: bounce;
  animation-duration: 2s;
  animation-timing-function: ease-in;

In this example, we have a ball that ‘bounces’ from the top of its container to 200px below its initial position. We set the animation-timing-function to ease-in, which means the animation starts slowly and gradually increases in speed, mimicking the natural acceleration of a falling object.

There are several predefined timing functions in CSS3, including linear, ease, ease-in, ease-out, ease-in-out, and step-start/end. For more control, you can use the cubic-bezier function to define your own custom timing function.

In practice, the animation-timing-function is pivotal in making animations feel more natural and less robotic. By allowing developers to define the pacing of animations, this property plays a key role in enhancing the user interface and overall user experience on the web. As front-end developers, understanding how to leverage animation-timing-function can greatly enhance the dynamism and realism of our animations.

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