ray()

Defines a path that is a line segment from the starting position of an element and proceeding in the direction defined by the specified angle. This value accepts up to three parameters – an <angle> similar to the CSS linear-gradient angle, a size value similar to the CSS radial-gradient size values, and the keyword contain. The angle 0deg starts on the y-axis, pointing up, with positive angles increasing in the clockwise direction. The possible values for the optional size parameter include closest-side, closest-corner, farthest-side, farthest-corner, and sides. If omitted, the value of the size parameter defaults to closest-side. The optional contain keyword reduces the length of the offset path so that the element stays within its containing block.

url()

References the ID of an SVG shape — circle, ellipse, line, path, polygon, polyline, or rect — using the shape's geometry as the path.

<basic-shape>

Specifies a CSS shape by using one of the shape functions such as circle(), ellipse(), inset(), polygon(), or path().

none

Specifies no motion path at all.

This property defines a path an animated element can follow. An offset path is either a specified path with one or multiple sub-paths or the geometry of a not-styled basic shape. The element's exact position on the offset path is determined by the offset-distance property. Each shape or path must define an initial position for the computed value of 0 for offset-distance and an initial direction which specifies the rotation of the object to the initial position.

Early versions of the spec called this property motion-path. It was changed to offset-path because the property describes static positions, not motion.

offset-path = 
  none                               |
  <ray()>                            |
  <path()>                           |
  <url>                              |
  [ <basic-shape> && <coord-box>? ]  |
  <coord-box>                        

<ray()> = 
  ray( [ <angle> && <size> && contain? ] )  

<path()> = 
  path( <string> )  

<url> = 
  url( <string> <url-modifier>* )  |
  src( <string> <url-modifier>* )  

<coord-box> = 
  content-box  |
  padding-box  |
  border-box   |
  fill-box     |
  stroke-box   |
  view-box     

<size> = 
  <extent-keyword>              |
  <length [0,∞]>                |
  <length-percentage [0,∞]>{2}  

<extent-keyword> = 
  closest-corner   |
  closest-side     |
  farthest-corner  |
  farthest-side    

<length-percentage> = 
  <length>      |
  <percentage>  

The offset-path properties in the CSS code sample defines a motion path that is identical to the <path> element in the SVG. The path, as can be seen in the rendering of the SVG code, is a line drawing of a house with a chimney.

SVG

The top and bottom halves of the scissors would appear in the top left of the canvas were they not positioned along the starting point of the motion path defined by offset-path.

<svg
  xmlns="http://www.w3.org/2000/svg"
  width="700"
  height="450"
  viewBox="350 0 1400 900">
  <title>House and Scissors</title>
  <rect x="595" y="423" width="610" height="377" fill="blue" />
  <polygon points="506,423 900,190 1294,423" fill="yellow" />
  <polygon points="993,245 993,190 1086,190 1086,300" fill="red" />
  <path
    id="house"
    d="M900,190 L993,245 V201 A11,11 0 0,1 1004,190 H1075 A11,11 0 0,1 1086,201 V300 L1294,423 H1216 A11,11 0 0,0 1205,434 V789 A11,11 0 0,1 1194,800 H606 A11,11 0 0,1 595,789 V434 A11,11 0 0,0 584,423 H506 L900,190"
    fill="none"
    stroke="black"
    stroke-width="13"
    stroke-linejoin="round"
    stroke-linecap="round" />
  <path
    id="firstScissorHalf"
    class="scissorHalf"
    d="M30,0 H-10 A10,10 0 0,0 -20,10 A20,20 0 1,1 -40,-10 H20 A10,10 0 0,1 30,0 M-40,20 A10,10 1 0,0 -40,0 A10,10 1 0,0 -40,20 M0,0"
    transform="translate(0,0)"
    fill="green"
    stroke="black"
    stroke-width="5"
    stroke-linejoin="round"
    stroke-linecap="round"
    fill-rule="evenodd" />
  <path
    id="secondScissorHalf"
    class="scissorHalf"
    d="M30,0 H-10 A10,10 0 0,1 -20,-10 A20,20 0 1,0 -40,10 H20 A10,10 0 0,0 30,0 M-40,-20 A10,10 1 0,0 -40,0 A10,10 1 0,0 -40,-20 M0,0"
    transform="translate(0,0)"
    fill="forestgreen"
    stroke="black"
    stroke-width="5"
    stroke-linejoin="round"
    stroke-linecap="round"
    fill-rule="evenodd" />
</svg>

CSS

.scissorHalf {
  offset-path: path(
    "M900,190  L993,245 V201  A11,11 0 0,1 1004,190  H1075  A11,11 0 0,1 1086,201  V300  L1294,423 H1216  A11,11 0 0,0 1205,434  V789  A11,11 0 0,1 1194,800  H606  A11,11 0 0,1 595,789  V434  A11,11 0 0,0 584,423  H506 L900,190"
  );
  animation: followpath 4s linear infinite;
}

@keyframes followpath {
  to {
    motion-offset: 100%;
    offset-distance: 100%;
  }
}

Result

• offset
• offset-distance
• offset-rotate
• SVG <path>
• path()

Other demos:

• Examples of the various values
• Triangle
• Scissors
• Eyes