CSS の transition-timing-function プロパティは、トランジション効果の作用を受ける CSS プロパティにおいて、中間状態の値を算出する方法を設定するために使用されます。


この加速曲線は、トランジションが行われるプロパティごとに 1 つの <timing-function> を用いて定義されます。

複数のタイミング関数を指定することができます。それぞれのタイミング関数は、 transition-property で指定されたように対応するプロパティに適用され、 transition-property のリストとして振るまいます。指定されたタイミング関数が transition-property のリストより少ない場合は、ユーザーエージェントはリスト内の値をそれぞれのトランジションプロパティのうちの値になるまで繰り返してどの値が使用されるかを計算します。関数の数が多い場合は、リストを適切な長さに切り詰めます。どちらの場合も、 CSS の宣言として妥当です。


/* キーワード値 */
transition-timing-function: ease;
transition-timing-function: ease-in;
transition-timing-function: ease-out;
transition-timing-function: ease-in-out;
transition-timing-function: linear;
transition-timing-function: step-start;
transition-timing-function: step-end;

/* 関数値 */
transition-timing-function: steps(4, jump-end);
transition-timing-function: cubic-bezier(0.1, 0.7, 1.0, 0.1);

/* 段階式の関数のキーワード */
transition-timing-function: steps(4, jump-start);
transition-timing-function: steps(10, jump-end);
transition-timing-function: steps(20, jump-none);
transition-timing-function: steps(5, jump-both);
transition-timing-function: steps(6, start);
transition-timing-function: steps(8, end);

/* 複数のタイミング関数 */
transition-timing-function: ease, step-start, cubic-bezier(0.1, 0.7, 1.0, 0.1);

/* グローバル値 */
transition-timing-function: inherit;
transition-timing-function: initial;
transition-timing-function: unset;

各々の <timing-function>transition-property で指定された、トランジションを行うプロパティに対応するタイミング関数を表します。

非段階のキーワード値 (ease, linear, ease-in-out, など) はそれぞれ4つの固定点による二次元ベジェ曲線を表しており、 cubic-bezier() 関数の値は定義済みの値以外を使用することができます。 The step timing functions divides the input time into a specified number of intervals that are equal in length. It is defined by a number of steps and a step position.

Equal to cubic-bezier(0.25, 0.1, 0.25, 1.0), the default value, increases in velocity towards the middle of the transition, slowing back down at the end.
Equal to cubic-bezier(0.0, 0.0, 1.0, 1.0), transitions at an even speed.
Equal to cubic-bezier(0.42, 0, 1.0, 1.0), starts off slowly, with the transition speed increasing until complete.
Equal to cubic-bezier(0, 0, 0.58, 1.0), starts transitioning quickly, slowing down the transition continues. •
Equal to cubic-bezier(0.42, 0, 0.58, 1.0), starts transitioning slowly, speeds up, and then slows down again.
cubic-bezier(p1, p2, p3, p4)
An author defined cubic-Bezier curve, where the p1 and p3 values must be in the range of 0 to 1.
steps( n, <jumpterm>)
Displays the transition along n stops along the transition, displaying each stop for equal lengths of time. For example, if n is 5,  there are 5 steps. Whether the transition holds temporarily at 0%, 20%, 40%, 60% and 80%, on the 20%, 40%, 60%, 80% and 100%, or makes 5 stops between the 0% and 100% along the transition, or makes 5 stops including the 0% and 100% marks (on the 0%, 25%, 50%, 75%, and 100%) depends on which of the following jump terms is used:
Denotes a left-continuous function, so that the first jump happens when the transition begins;
Denotes a right-continuous function, so that the last jump happens when the animation ends;
There is no jump on either end. Instead, holding at both the 0% mark and the 100% mark, each for 1/n of the duration
Includes pauses at both the 0% and 100% marks, effectively adding a step during the transition time.
Same as jump-start.
Same as jump-end.
Equal to steps(1, jump-start)
Equal to steps(1, jump-end)



<easing-function> = linear | <cubic-bezier-timing-function> | <step-timing-function>

<cubic-bezier-timing-function> = ease | ease-in | ease-out | ease-in-out | cubic-bezier([0,1]>, <number>, [0,1]>, <number>)
<step-timing-function> = step-start | step-end | steps(<integer>[, <step-position>]?)

<step-position> = jump-start | jump-end | jump-none | jump-both | start | end

Cubic-Bezier examples

.ease {
   transition-timing-function: ease;
.easein {
   transition-timing-function: ease-in;
.easeout {
   transition-timing-function: ease-out;
.easeinout {
   transition-timing-function: ease-in-out;
.linear {
   transition-timing-function: linear;
.cb {
   transition-timing-function: cubic-bezier(0.2,-2,0.8,2);

Step examples

.jump-start {
   transition-timing-function: steps(5, jump-start);
.jump-end {
   transition-timing-function: steps(5, jump-end);
.jump-none {
   transition-timing-function: steps(5, jump-none);
.jump-both {
   transition-timing-function: steps(5, jump-both);
.step-start {
   transition-timing-function: step-start;
.step-end {
   transition-timing-function: step-end;


Some animations can be helpful such as to guide users to understand what actions are expected, to show relationships within the user interface, and to inform users as to what actions have occurred. Animations can help reduce cognitive load, prevent change blindness, and establish better recall in spatial relationships. However, some animations can be problematic for people with cognitive concerns such as Attention Deficit Hyperactivity Disorder (ADHD) and certain kinds of motion can be a trigger for Vestibular disorders, epilepsy, and migraine and Scotopic sensitivity.

Consider providing a mechanism for pausing or disabling animation, as well as using the Reduced Motion Media Query to create a complimentary experience for users who have expressed a preference for no animated experiences.


仕様書 状態 備考
CSS Transitions
transition-timing-function の定義
草案 初回定義

適用対象すべての要素、::before / ::after 擬似要素


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