<length-percentage>

Specifies the <length-percentage> values for the x and y coordinates of the rectangle.

<length-percentage [0,∞]>

Specifies non-negative <length-percentage> values for the width and height of the rectangle. The minimum value can be zero, and the maximum value has no limit.

round <'border-radius'>

Specifies the radius of the rounded corners of the rectangle using the same syntax as the CSS border-radius shorthand property. This parameter is optional.

In the example below, the offset-path property uses the xywh() function to define the shape of the path on which the element, a magenta box in this case, moves. Two different scenarios are shown, each with different values for the xywh() function. The arrow inside the boxes points to the right edge of the box.

<div class="container">
  Rectangular path 1
  <div class="path xywh-path-1">→</div>
</div>
<div class="container">
  Rectangular path 2
  <div class="path xywh-path-2">→</div>
</div>

.container {
  position: relative;
  display: inline-block;
  width: 200px;
  height: 200px;
  border: 1px solid black;
  margin: 30px;
  text-align: center;
}

.path {
  width: 50px;
  height: 50px;
  position: absolute;
  background-color: magenta;
  animation: move 10s linear infinite;
}

.xywh-path-1 {
  offset-path: xywh(20px 20px 100% 100% round 10%);
}

.xywh-path-2 {
  offset-path: xywh(20px 30% 150% 200%);
}

@keyframes move {
  0% {
    offset-distance: 0%;
  }
  100% {
    offset-distance: 100%;
  }
}

Result

• The path 1 rectangle is offset by 20px from the left and top edges of the containing block. This path rectangle has the same dimension as the containing block, that is, the width is 100% of the width of the containing block, and the height is 100% of the height of the containing block. Notice how the arrow inside the box follows the 10% curve (defined by round 10%) at the rectangular path corners.
• As the upper limit of both width and height in xywh() is infinity, setting the height to 200% in the path 2 rectangle makes the generated rectangle twice as tall as the containing block. Notice how the arrow inside the box behaves at the corners when no round <'border-radius'> is specified.

• inset() function
• rect() function
• clip-path property
• offset-path property
• <basic-shape> data type
• CSS shapes module
• Guide to basic shapes