The transition-timing-function CSS property is used to specify the timing function that determines how the intermediate property values are calculated during a CSS transition. It controls the speed and pace of the transition effect, allowing you to create different acceleration or deceleration patterns.

The transition-timing-function property accepts various predefined keywords or cubic Bézier curve functions:

  • Predefined keywords: These keywords represent common timing functions and provide consistent easing effects. Some examples include ease (default), linear, ease-in, ease-out, and ease-in-out.
  • Cubic Bézier functions: These functions allow for more precise control over the timing function by defining custom acceleration curves using four values: cubic-bezier(x1, y1, x2, y2). Each value represents the control points of the cubic Bézier curve.

Here’s an example:

.button {
  transition-timing-function: ease-in-out;

In this example, the .button class sets the transition-timing-function property to ease-in-out, which applies an equal acceleration and deceleration effect to the transition, creating a smooth and balanced easing.

It’s important to note that the transition-timing-function property affects the entire transition duration and is applied to all properties being transitioned unless specified individually.

The transition-timing-function property is commonly used in combination with other transition-related properties, such as transition-property, transition-duration, and transition-delay. Together, these properties allow for the creation of smooth and controlled transitions between different states of an element.

By choosing different timing functions, you can control the visual effect of the transition, whether it’s a gradual start (ease-in), gradual end (ease-out), or a combination of both (ease-in-out). Cubic Bézier functions provide even more flexibility, allowing for custom timing curves tailored to specific design requirements.

Remember to consider the overall user experience and the desired visual effect when selecting a timing function. Smooth and natural transitions can enhance the usability and aesthetics of a website or application, while abrupt or overly complex transitions can be jarring or distracting.