CSS Transitions

There are two ways to create animations with pure CSS:  CSS animations and CSS transitions.  CSS transitions provide a simple method for animation one or multiple properties from one value to another.    CSS transitions do not require @keyframes -- simply provide the desired transition properties to a selector.  CSS transitions traditionally occur upon state changes, like :hover or :focus.

A Basic CSS Transitions

Let's create a basic CSS transition of opacity (a fade in and out):

/* from */
.myElement {
	opacity: 0.5;
	transition-property: opacity;
}

/* to */
.myElement:hover {
	opacity: 1;
}

In the example above, when the element is hovered over, its opacity animates from 50% opacity to 100% opacity.  When the mouse leaves the element, its opacity animates back down to 50%.

CSS Transition Properties

Outside of simply providing a CSS property to transition, there are a number of other helpful transition properties:

• transition-property: one or more properties, or "all", to transition
• transition-duration: amount of time the transition should take to complete (ex: 2s or 0.5s)
• transition-delay: delay before starting the transition
• transition-timing-function: traditional timing curve function for the transition

These transition properties allow complete control over the simple animation.  Here's a CSS transition example using all of the properties available:

/* from */
.myElement {
	color: #333;

	transition-property: color;
	transition-duration: 1s;
	transition-delay: .2s;
	transition-timing-function: linear;
}

/* to */
.myElement:focus {
	color: #999;
}

/* shorthand: property duration timingFunc delay */
.myElement {
	transition: all 2s linear 0.3s;
}

In most cases, the default duration, delay,and timing function wont need to be changed.

Transitioning Multiple Properties

Multiple transition properties should be separated by commas:

.myElement {
	/* padding-left, opacity, height, and color here */

	transition-property: padding-left, opacity, height, color;
	transition-duration: 1s, 2s, 3s, 4s;
}

The "all" keyword can also be used to signify all properties should be transformed.  Separate transitions may also be strung together in a shorthand syntax:

.myElement {
	transition: padding-left 1s, opacity 2s, height 3s, color: 4s;
}

The property value can get quite long, but the flexibility is quite nice!

Detecting Transition End with JavaScript

If you're looking to detect transition end with JavaScript, that's quite easy:

myElement.addEventListener("transitionend", function() {

	// Do something now that the transition has ended

}, true);

The transitionend event on the node will fire once the transition has completed.

CSS Transition Examples

My blog has featured a number of CSS transition examples:

• CSS Kwicks (demo)
• CSS Flip Animation (demo)
• CSS 3D Folding Animation (demo)
• CSS PhotoStack (demo)