Introduction
The @keyframes CSS at-rule controls
the intermediate steps in a CSS animation sequence by defining
styles for keyframes (or waypoints) along the animation sequence.
This gives more control over the intermediate steps of the animation
sequence than transitions.
Syntax
@keyframes slidein {
from {
transform: translateX(0%);
}
to {
transform: translateX(100%);
}
}
Values
-
<custom-ident>- A name identifying the keyframe list. This must match the identifier production in CSS syntax.
-
from- A starting offset of 0%
-
to- An ending offset of 100%
-
<percentage>- A percentage of the time through the animation sequence at which the specified keyframe should occur.
Description
Javascript can access the @keyframes at-rule with the
CSS object model interface CSSKEYframesRule.
To use keyframes, create a @keyframes rule with a name
that is then used by the animation-name property to
match an animation to its keyframe declaration. Each
@keyframes rule contains a style list of keyframe
selectors, which specify percentages along the animation when the
keyframe occurs, and a block containing the styles for that
keyframe.
You can list the keyframe percentages in any order; they will be handled in the order they should occur.
Valid keyframes lists
If a keyframe rule doesn't specify the start or end states of the
animation (this is, 0%/from and 100%/to),
browsers will use the element's existing styles for the start/end
states. This can be used to animate an element from its initial
state and back.
Properties that can't be animated in keyframe rules are ignored, but supported properties will still be animated.
Resolving Duplicates
If multiple keyframe sets exist for a given name, the last one
encountered by the parser is used. @keyframes rules
don't cascade, so animations never derive keyframes from more than
one rule set.
If a given animation time offset is duplicated, all keyframes in the
@keyframes rule for that percentage are used for that
frame. There is cascading within a @keyframes rule if
multiple keyframes specify the same percentage values.
When Properties are left out of some keyframes
Properties that aren't specified in every keyframe are interpolated if possible - properties that can't be interpolated are dropped from the animation. For example:
@keyframes identifier {
0% {top: 0; left: 0;}
30% {top: 50px;}
68%, 72% {left: 50px;}
100% {top: 100px; left: 100%;}
}
Here, the top property animates using the 0%,
30%, and 100% keyframes, and left animates
using the 0%, 68%, 72%, and
100% keyframes.
When a keyframe is defined multiple times
If a keyframe is defined multiple times but not all affected properties are in each keyframe, all values specified in these keyframes are considered. For example:
@keyframes identifier {
0% {top: 0;}
50% {top: 30px; left: 20px;}
50% {top: 10px;}
100% {top: 0;}
}
In this example, at the 50% keyframe, the values used
are top: 10px and left: 20px.
important in a keyframe
Declarations in a keyframe qualified with
!important are ignored.
@keyframes important1 {
from {margin-top: 50px;}
50% {margin-top: 150px !important;} /* ignored */
to {margin-top: 100px;}
}
@keyframes important2 {
from {margin-top: 50px;
margin-bottom: 100px;}
to {margin-top: 150px !important; /* ignored */
margin-bottom: 50px;}
}
Formal Syntax
@keyframes <keyframes-name> {
<keyframe-block-list>
}
where
<keyframes-name> = <custom-ident> |
<string>
<keyframe-block-list> = <keyframe-block>+
where
<keyframe-block> = <keyframe-selector># {
<declaration-list>
}
where
<keyframe-selector> = from | to | <percentage>
Reference
All the documentation on this page is taken from Mozilla Developer Network