Selecting the transition timing function

Timing Function Selection for Transitions

The timing function is one of the core parameters of CSS transition effects, determining the rate of change for property values during the transition. Common preset functions include linear, ease, ease-in, ease-out, and ease-in-out, but developers can also customize more complex change patterns using Bézier curves.

.box {
  transition: width 2s cubic-bezier(0.68, -0.6, 0.32, 1.6);
}

Detailed Explanation of Preset Timing Functions

The linear function produces a constant-speed change effect, suitable for mechanical motion scenarios. ease, as the default value, presents a slow start, acceleration, and then deceleration, aligning with most natural motion patterns. ease-in emphasizes a slow start, ideal for scenes where objects accelerate away; ease-out highlights the deceleration at the end, suitable for objects coming to a stop.

/* Comparison examples of different preset functions */
.item1 { transition-timing-function: linear; }
.item2 { transition-timing-function: ease; }
.item3 { transition-timing-function: ease-in; }
.item4 { transition-timing-function: ease-out; }
.item5 { transition-timing-function: ease-in-out; }

Customization with Bézier Curves

When preset functions fall short, the cubic-bezier() function can define a cubic Bézier curve. This function accepts four parameters between 0 and 1, representing the coordinates of two control points. For example, cubic-bezier(0.1, 0.7, 0.1, 1) creates a noticeable elastic effect.

/* Elastic effect implementation */
.spring-effect {
  transition: transform 0.5s cubic-bezier(0.1, 0.7, 0.1, 1);
}

Application of Step Functions

The steps() function can create discrete transition effects, suitable for frame-by-frame animations or mechanical changes. The first parameter specifies the number of steps, and the optional second parameter determines whether the change occurs at the start (start) or end (end) of each interval.

/* Simulating a typewriter effect */
.typewriter {
  transition: width 1s steps(10, end);
}

Performance Optimization Considerations

Complex timing functions may trigger repaint issues. When handling expensive properties like box-shadow or filter, it's recommended to use the will-change property to inform the browser in advance:

.optimized {
  will-change: transform;
  transition: transform 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

Responsive Scenario Adaptation

On mobile devices, it's often necessary to shorten transition durations and simplify timing functions. Adjustments can be made via media queries:

@media (max-width: 768px) {
  .responsive {
    transition-duration: 0.3s;
    transition-timing-function: ease-out;
  }
}

Compound Transition Control

Different properties can use different timing functions to achieve richer effects. For example, a button hover might use ease-in-out for color gradients and ease-out for shadow changes:

.button {
  transition: 
    background-color 0.4s ease-in-out,
    box-shadow 0.2s ease-out;
}

Debugging Tool Tips

Chrome DevTools' Animations panel allows real-time editing of Bézier curves. Drag the control points to observe changes and copy the generated cubic-bezier() values directly into your code:

// Quick testing in the console
document.querySelector('.test').style.transitionTimingFunction = 
  'cubic-bezier(0.17, 0.67, 0.83, 0.67)';

Physical Motion Simulation

Combining multiple transitions can simulate more realistic physical effects. For example, free-fall motion requires initial acceleration (ease-in) and a bounce upon landing:

.falling-object {
  transition: 
    transform 0.8s cubic-bezier(0.55, 0, 0.85, 0.36),
    opacity 0.3s ease-out;
}

User Preference Adaptation

Respect user system settings for reduced motion preferences:

@media (prefers-reduced-motion: reduce) {
  .motion-element {
    transition: none;
  }
}