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offset-anchor

The offset-anchor CSS property specifies the point inside the box of an element travelling along an offset-path that is actually moving along the path.

Syntax

/* Keyword values */
offset-anchor: top;
offset-anchor: bottom;
offset-anchor: left;
offset-anchor: right;
offset-anchor: center;
offset-anchor: auto;

/* <percentage> values */
offset-anchor: 25% 75%;

/* <length> values */
offset-anchor: 0 0;
offset-anchor: 1cm 2cm;
offset-anchor: 10ch 8em;

/* Edge offsets values */
offset-anchor: bottom 10px right 20px;
offset-anchor: right 3em bottom 10px;

/* Global values */
offset-anchor: inherit;
offset-anchor: initial;
offset-anchor: unset;

Values

auto
offset-anchor is given the same value as the element's transform-origin, unless offset-path is none, in which case it takes its value from offset-position.
<position>
A <position> defines an x/y coordinate, to place an item relative to the edges of an element's box. It can be defined using one to four values. For more specifics, see the <position> and background-position reference pages. Note that the 3-value position syntax does not work for any usage of <position>, except for in background(-position).

Formal definition

Initial value auto
Applies to transformable elements
Inherited no
Percentages relativeToWidthAndHeight
Computed value for <length> the absolute value, otherwise a percentage
Animation type a position

Formal syntax

auto | <position>

where
<position> = [ [ left | center | right ] || [ top | center | bottom ] | [ left | center | right | <length-percentage> ] [ top | center | bottom | <length-percentage> ]? | [ [ left | right ] <length-percentage> ] && [ [ top | bottom ] <length-percentage> ] ]

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

Examples

Setting various offset-anchor values

In the following example, we have three <div> elements nested in <section> elements. Each <div> is given the same offset-path (a horizontal line 200 pixels long) and animated to move along it. The three are then given different background-color and offset-anchor values.

Each <section> has been styled with a linear gradient to give it a horizontal line running through its center, to give you a visual display of where the <div>'s offset paths are running.

This allows you to see what effect the different offset-anchor values have — the first one, auto, causes the <div>'s center point to move along the path. The other two cause the <div>'s top-right and bottom-left points to move along the path, respectively.

HTML

<section>
  <div class="offset-anchor1"></div>
</section>
<section>
  <div class="offset-anchor2"></div>
</section>
<section>
  <div class="offset-anchor3"></div>
</section>

CSS

div {
  offset-path: path('M 0,20 L 200,20');
  animation: move 3000ms infinite alternate ease-in-out;
  width: 40px;
  height: 40px;
}

section {
  background-image: linear-gradient(to bottom, transparent, transparent 49%, #000 50%, #000 51%, transparent 52%);
  border: 1px solid #ccc;
  margin-bottom: 10px;
}

.offset-anchor1 {
  offset-anchor: auto;   
  background: cyan;
}

.offset-anchor2 {
  offset-anchor: right top;
  background: purple;
}

.offset-anchor3 {
  offset-anchor: left bottom;
  background: magenta;
}

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

Result

Specifications

Specification Status Comment
Motion Path Module Level 1
The definition of 'offset-anchor' in that specification.
Working Draft Initial definition

Browser compatibilityUpdate compatibility data on GitHub

Desktop
Chrome Edge Firefox Internet Explorer Opera Safari
offset-anchor 79 79 72
72
70 — 72
Disabled
Disabled From version 70 until version 72 (exclusive): this feature is behind the layout.css.motion-path.enabled preference (needs to be set to true). To change preferences in Firefox, visit about:config.
No No No
Mobile
Android webview Chrome for Android Firefox for Android Opera for Android Safari on iOS Samsung Internet
offset-anchor 79 79 No No No 12.0

See also

© 2005–2020 Mozilla and individual contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/CSS/offset-anchor