clip-path

/* Keyword values */
clip-path: none;

/* Image values */ 
clip-path: url(resources.svg#c1

/* Box values */
clip-path: fill-box;
clip-path: stroke-box;
clip-path: view-box;
clip-path: margin-box;
clip-path: border-box;
clip-path: padding-box;
clip-path: content-box;

/* Geometry values */
clip-path: inset(100px 50px
clip-path: circle(50px at 0 100px
clip-path: polygon(50% 0%, 100% 50%, 50% 100%, 0% 50%

/* Box and geometry values combined */
clip-path: padding-box circle(50px at 0 100px

/* Global values */
clip-path: inherit;
clip-path: initial;
clip-path: unset;

<clip-source> | [ <basic-shape> || <geometry-box> ] | nonewhere 
<clip-source> = <url>
<basic-shape> = <inset()> | <circle()> | <ellipse()> | <polygon()>
<geometry-box> = <shape-box> | fill-box | stroke-box | view-box
where 
<inset()> = inset( <length-percentage>{1,4} [ round <border-radius> ]? )
<circle()> = circle( [ <shape-radius> ]? [ at <position> ]? )
<ellipse()> = ellipse( [ <shape-radius>{2} ]? [ at <position> ]? )
<polygon()> = polygon( <fill-rule>? , [ <length-percentage> <length-percentage> ]# )
<shape-box> = <box> | margin-box
where 
<length-percentage> = <length> | <percentage>
<shape-radius> = <length-percentage> | closest-side | farthest-side
<position> = [[ left | center | right | top | bottom | <length-percentage> ] | [ left | center | right | <length-percentage> ] [ top | center | bottom | <length-percentage> ] | [ center | [ left | right ] <length-percentage>? ] && [ center | [ top | bottom ] <length-percentage>? ]]
<fill-rule> = nonzero | evenodd
<box> = border-box | padding-box | content-box

/* Inline SVG  */
.target {
  clip-path: url(#c1
}

/* External SVG */
.anothertarget {
  clip-path: url(resources.svg#c1
}

/* Circle shape */
.circleClass {
  clip-path: circle(15px at 20px 20px
}

<img id="clipped" src="https://mdn.mozillademos.org/files/12668/MDN.svg"
    alt="MDN logo">
<svg height="0" width="0">
  <defs>
    <clipPath id="cross">
      <rect y="110" x="137" width="90" height="90"/>
      <rect x="0" y="110" width="90" height="90"/>
      <rect x="137" y="0" width="90" height="90"/>
      <rect x="0" y="0" width="90" height="90"/>
    </clipPath>
  </defs>
</svg>

<select id="clipPath">
  <option value="none">none</option>
  <option value="circle(100px at 110px 100px)">circle</option>
  <option value="url(#cross)" selected>cross</option>
  <option value="inset(20px round 20px)">inset</option>
</select>

#clipped {
  margin-bottom: 20px;
  clip-path: url(#cross
}