ant-design/style/components/switch.less

@switch-prefix-cls:ant-switch;

@switch-duration:.3s;

.@{switch-prefix-cls} {
  position: relative;
  display: inline-block;
  box-sizing: border-box;
  width: 44px;
  height: 22px;
  line-height: 20px;
  vertical-align: middle;
  border-radius: 20px 20px;
  border: 1px solid #ccc;
  background-color: #ccc;
  cursor: pointer;
  transition: all @switch-duration @ease-in-out-circ;
  user-select: none;

  &-inner {
    color: #fff;
    font-size: 12px;
    position: absolute;
    left: 24px;
  }

  &:after {
    position: absolute;
    width: 18px;
    height: 18px;
    left: 2px;
    top: 1px;
    border-radius: 100%;
    background-color: #fff;
    content: " ";
    cursor: pointer;
    transition: left @switch-duration @ease-in-out-circ;
  }

  &-small {
    height: 14px;
    line-height: 12px;
    width: 28px;
    &:after {
      width: 12px;
      height: 12px;
      top: 0;
      left: 0;
    }
  }

  &-small&-checked:after {
    left: 14px;
  }

  &-checked {
    border: 1px solid @primary-color;
    background-color: @primary-color;

    .@{switch-prefix-cls}-inner {
      left: 6px;
    }

    &:after {
      left: 22px;
    }
  }

  &-disabled {
    cursor: not-allowed;
    background: #f4f4f4;
    border-color: #f4f4f4;

    &:after {
      background: #ccc;
      cursor: not-allowed;
    }

    &-inner {
      color: #ccc;
    }
  }
}