CSS transitions allows you to change property values smoothly, over a given duration.

How to Use CSS Transitions?

To create a transition effect, you must specify two things:

- the CSS property you want to add an effect to
- the duration of the effect

Note: If the duration part is not specified, the transition will have no effect, because the default value is 0.

The following example shows a 100px * 100px red <div> element. The <div> element has also specified a transition effect for the width property, with a duration of 2 seconds:

EXAMPLE:

div {
width: 100px;
height: 100px;
background: red;
transition: width 2s;
}

The transition effect will start when the specified CSS property (width) changes value.

Now, let us specify a new value for the width property when a user mouses over the <div> element:

EXAMPLE:

div:hover {
width: 300px;
}

Notice that when the cursor mouses out of the element, it will gradually change back to its original style.

Change Several Property Values

The following example adds a transition effect for both the width and height property, with a duration of 2 seconds for the width and 4 seconds for the height:

EXAMPLE:

div {
transition: width 2s, height 4s;
}

Specify the Speed Curve of the Transition

The transition-timing-function property specifies the speed curve of the transition effect.

The transition-timing-function property can have the following values:

ease - specifies a transition effect with a slow start, then fast, then end slowly (this is default)
linear - specifies a transition effect with the same speed from start to end
ease-in - specifies a transition effect with a slow start
ease-out - specifies a transition effect with a slow end
ease-in-out - specifies a transition effect with a slow start and end
cubic-bezier(n,n,n,n) - lets you define your own values in a cubic-bezier function

The following example shows the some of the different speed curves that can be used:

EXAMPLE:

#div1 {transition-timing-function: linear;}
#div2 {transition-timing-function: ease;}
#div3 {transition-timing-function: ease-in;}
#div4 {transition-timing-function: ease-out;}
#div5 {transition-timing-function: ease-in-out;}

Delay the Transition Effect

The transition-delay property specifies a delay (in seconds) for the transition effect.

The following example has a 1 second delay before starting:

EXAMPLE:

div {
transition-delay: 1s;
}

Transition + Transformation

The following example adds a transition effect to the transformation:

EXAMPLE:

div {
transition: width 2s, height 2s, transform 2s;
}

More Transition Examples

The CSS transition properties can be specified one by one, like this:

EXAMPLE:

div {
transition-property: width;
transition-duration: 2s;
transition-timing-function: linear;
transition-delay: 1s;
}

or by using the shorthand property transition:

EXAMPLE:

div {
transition: width 2s linear 1s;

}