keyframes

关键帧

编排多阶段关键帧、插值、步进与结束状态。

预览

动画中预先定义的节点（如 0%、50%、100%），浏览器会补全节点之间的画面。

关键帧

实现「关键帧」：编排多阶段关键帧、插值、步进与结束状态。参数设为演示时长 720ms、编排方式 keyframes、步数 4、结束状态 both、曲线 soft。在状态发生变化时触发一次，并允许重新播放。使用语义化 HTML，CSS 作用域限定在 .motion-demo--keyframes。为 prefers-reduced-motion 和 .force-reduced-motion 提供等价的低动态方案。

markup.html

<div class="motion-demo motion-demo--keyframes" data-motion="keyframes" aria-label="关键帧 示例">
  <article class="motion-surface">
    <strong>关键帧</strong>
    <span class="motion-line"></span>
    <span class="motion-line"></span>
  </article>
</div>

motion.css

.motion-demo.motion-demo--keyframes {
  box-sizing: border-box;
  position: relative;
  display: grid;
  place-items: center;
  width: min(100%, 34rem);
  min-height: 15rem;
  padding: 2rem;
  overflow: hidden;
  color: #18181b;
  background: #fafafa;
  border: 1px solid #e4e4e7;
  border-radius: 16px;
  isolation: isolate;
}

.motion-demo.motion-demo--keyframes *, .motion-demo.motion-demo--keyframes *::before, .motion-demo.motion-demo--keyframes *::after {
  box-sizing: border-box;
}

.motion-demo.motion-demo--keyframes .motion-surface {
  position: relative;
  display: grid;
  gap: 0.65rem;
  width: min(100%, 18rem);
  padding: 1.25rem;
  background: #ffffff;
  border: 1px solid #e4e4e7;
  border-radius: 16px;
  box-shadow: none;
}

.motion-demo.motion-demo--keyframes .motion-surface strong { font-weight: 500; }

.motion-demo.motion-demo--keyframes .motion-line {
  display: block;
  width: 100%;
  height: 0.5rem;
  background: #e4e4e7;
  border-radius: 999px;
}

.motion-demo.motion-demo--keyframes .motion-line:last-child { width: 62%; }

.motion-demo.motion-demo--keyframes .motion-button {
  position: relative;
  min-height: 2.75rem;
  padding: 0.75rem 1.1rem;
  color: white;
  font: inherit;
  font-weight: 700;
  background: #18181b;
  border: 0;
  border-radius: 999px;
  cursor: pointer;
}

.motion-demo.motion-demo--keyframes .motion-button:focus-visible { outline: 3px solid rgb(37 99 235 / 32%); outline-offset: 3px; }

.motion-demo.motion-demo--keyframes .motion-action-row {
  display: flex;
  justify-content: center;
  gap: 0.5rem;
  margin-top: 0.85rem;
}

.motion-demo.motion-demo--keyframes .motion-replay-scene {
  width: min(100%, 22rem);
  display: grid;
  place-items: center;
}

.motion-demo.motion-demo--keyframes .motion-pausable-scene {
  width: min(100%, 22rem);
  display: grid;
  place-items: center;
}

.motion-demo.motion-demo--keyframes button.motion-surface {
  color: inherit;
  font: inherit;
  text-align: start;
  cursor: pointer;
}

.motion-demo.motion-demo--keyframes .motion-replay-button,
.motion-demo.motion-demo--keyframes .motion-undo-button,
.motion-demo.motion-demo--keyframes .motion-dismiss-button,
.motion-demo.motion-demo--keyframes .motion-pause-button {
  min-height: 2.75rem;
  padding: 0.65rem 0.9rem;
  color: #18181b;
  font: 650 0.78rem/1 ui-sans-serif, system-ui, sans-serif;
  background: #ffffff;
  border: 1px solid #d4d4d8;
  border-radius: 8px;
  cursor: pointer;
}

.motion-demo.motion-demo--keyframes .motion-replay-button:focus-visible,
.motion-demo.motion-demo--keyframes .motion-undo-button:focus-visible,
.motion-demo.motion-demo--keyframes .motion-dismiss-button:focus-visible,
.motion-demo.motion-demo--keyframes .motion-pause-button:focus-visible,
.motion-demo.motion-demo--keyframes [data-reorder-item]:focus-visible,
.motion-demo.motion-demo--keyframes [data-swipe-target]:focus-visible {
  outline: 3px solid rgb(37 99 235 / 32%);
  outline-offset: 3px;
}

.motion-demo.motion-demo--keyframes .motion-status {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

.motion-demo.motion-demo--keyframes .motion-ripple-ink {
  position: absolute;
  width: 12px;
  height: 12px;
  pointer-events: none;
  background: rgb(255 255 255 / 72%);
  border-radius: 50%;
  transform: translate(-50%, -50%) scale(0.95);
  opacity: 0;
}

.motion-demo.motion-demo--keyframes .motion-state-stack { position: relative; width: min(100%, 18rem); height: 9rem; }
.motion-demo.motion-demo--keyframes .motion-state { position: absolute; inset: 0; display: grid; place-items: center; padding: 1rem; background: #ffffff; border: 1px solid #e4e4e7; border-radius: 16px; }
.motion-demo.motion-demo--keyframes .motion-state--to { background: #18181b; color: white; }

.motion-demo.motion-demo--keyframes .motion-scroll-track > span { color: #71717a; font: 600 0.72rem/1.2 ui-monospace, monospace; letter-spacing: 0.08em; text-transform: uppercase; }
.motion-demo.motion-demo--keyframes .motion-orbit-item { display: grid; place-items: center; width: 2.5rem; height: 2.5rem; color: white; background: #2563eb; border-radius: 50%; }
.motion-demo.motion-demo--keyframes .motion-text-stack { position: relative; width: min(100%, 18rem); min-height: 4rem; }
.motion-demo.motion-demo--keyframes svg { width: min(100%, 20rem); height: auto; }

.motion-demo.motion-demo--keyframes .motion-surface { animation: motion-keyframes 720ms cubic-bezier(0.23, 1, 0.32, 1) 0ms 1 both; }
@keyframes motion-keyframes { 0% { opacity: 0.45; transform: translateX(-46px); } 50% { transform: translateX(46px) rotate(4deg); } 100% { opacity: 1; transform: translateX(46px); } }

@keyframes motion-keyframes-reduced-fade {
  from { opacity: 0.84; }
  to { opacity: 1; }
}

.force-reduced-motion .motion-demo.motion-demo--keyframes {
  animation: motion-keyframes-reduced-fade 160ms cubic-bezier(0.23, 1, 0.32, 1) both !important;
}

.force-reduced-motion .motion-demo.motion-demo--keyframes *,
.force-reduced-motion .motion-demo.motion-demo--keyframes *::before,
.force-reduced-motion .motion-demo.motion-demo--keyframes *::after {
  animation: none !important;
  animation-delay: 0ms !important;
  animation-iteration-count: 1 !important;
  transition-property: opacity, color, background-color, border-color !important;
  transition-duration: 160ms !important;
  transition-delay: 0ms !important;
  scroll-behavior: auto !important;
}

.force-reduced-motion .motion-demo.motion-demo--keyframes .motion-button,
.force-reduced-motion .motion-demo.motion-demo--keyframes [data-reorder-item],
.force-reduced-motion .motion-demo.motion-demo--keyframes [data-swipe-target],
.force-reduced-motion .motion-demo.motion-demo--keyframes [data-spring-target] {
  transform: none !important;
}

.force-reduced-motion .motion-demo.motion-demo--keyframes .motion-path { stroke-dashoffset: 0 !important; }
.force-reduced-motion .motion-demo.motion-demo--keyframes .motion-word--from { opacity: 0 !important; visibility: hidden; }
.force-reduced-motion .motion-demo.motion-demo--keyframes .motion-word:not(.motion-word--from) { opacity: 1 !important; filter: none !important; transform: none !important; }

@media (prefers-reduced-motion: reduce) {
  .motion-demo.motion-demo--keyframes {
    animation: motion-keyframes-reduced-fade 160ms cubic-bezier(0.23, 1, 0.32, 1) both !important;
  }

  .motion-demo.motion-demo--keyframes *, .motion-demo.motion-demo--keyframes *::before, .motion-demo.motion-demo--keyframes *::after {
    animation: none !important;
    animation-delay: 0ms !important;
    animation-iteration-count: 1 !important;
    transition-property: opacity, color, background-color, border-color !important;
    transition-duration: 160ms !important;
    transition-delay: 0ms !important;
    scroll-behavior: auto !important;
  }

  .motion-demo.motion-demo--keyframes .motion-button,
  .motion-demo.motion-demo--keyframes [data-reorder-item],
  .motion-demo.motion-demo--keyframes [data-swipe-target],
  .motion-demo.motion-demo--keyframes [data-spring-target] {
    transform: none !important;
  }

  .motion-demo.motion-demo--keyframes .motion-path { stroke-dashoffset: 0 !important; }
  .motion-demo.motion-demo--keyframes .motion-word--from { opacity: 0 !important; visibility: hidden; }
  .motion-demo.motion-demo--keyframes .motion-word:not(.motion-word--from) { opacity: 1 !important; filter: none !important; transform: none !important; }
}

深入了解

实现前检查

目的: 定义多阶段状态、补间方式、步进节奏和动画结束后的样式。
频率: 适合低频、具有阶段含义的动作；简单反馈优先使用单段 transition。
触发: 由明确状态变化或演示重播触发，每个关键帧承担可解释的阶段。
进入 / 离开: 首帧对应进入前状态，末帧对应稳定状态；退出动画拥有独立且更短的时间线。
可打断性: 中断后根据当前计算样式建立新时间线，避免强制跳到某个关键帧。
手势与键盘: 时间线本身无需手势；交互式进度控制要支持指针、触摸和键盘。
减弱动效策略: 缩短为一次状态切换，移除预备、回弹和重复阶段。

可访问性

减弱动效

缩短为一次状态切换，移除预备、回弹和重复阶段。

参数参考

参数	范围 / 选项	默认值	作用
`duration`	300ms–2400ms	720ms	演示使用较长时长以便观察完整变化；生产界面的即时反馈应收敛到 300ms 内。
`mode`	关键帧 / 补间 / 步进	关键帧	选择编排方式。
`steps`	2–12	4	调节步数。
`fill`	无 / 保持结束 / 前后保持	前后保持	选择结束状态。
`ease`	柔和 / 清脆 / 平稳 / 匀速	柔和	控制速度随时间变化的方式。