- Firefox 54+
- Chrome 51+
- Edge 79+
- Safari 10+
To use the polyfill, add this script tag to your document <head>:
<script type="module">
if (!("anchorName" in document.documentElement.style)) {
import("https://unpkg.com/@oddbird/css-anchor-positioning");
}
</script>If you want to manually apply the polyfill, you can instead import the
polyfill function directly from the
@oddbird/css-anchor-positioning/dist/css-anchor-positioning-fn.js file.
For build tools such as Vite, Webpack, and Parcel, that will look like this:
import polyfill from '@oddbird/css-anchor-positioning/fn';The polyfill function returns a promise that resolves when the polyfill has
been applied.
You can view a more complete demo here.
The polyfill accepts one argument (type: boolean, default: false), which
determines whether anchor calculations should update on every animation
frame (e.g. when the
anchor element is animated using transforms), in addition to always updating
on scroll/resize. While this option is optimized for performance, it should be
used sparingly.
<script type="module">
if (!("anchorName" in document.documentElement.style)) {
const { default: polyfill } = await import("https://unpkg.com/@oddbird/css-anchor-positioning/dist/css-anchor-positioning-fn.js");
polyfill(true);
}
</script>When using the default version of the polyfill that executes automatically, this
option can be set by setting the value of
window.UPDATE_ANCHOR_ON_ANIMATION_FRAME.
<script type="module">
if (!("anchorName" in document.documentElement.style)) {
window.UPDATE_ANCHOR_ON_ANIMATION_FRAME = true;
import("https://unpkg.com/@oddbird/css-anchor-positioning");
}
</script>This polyfill was implemented against an early version of the spec, and updates were paused to allow the syntax to solidify. Now that browsers are working on implementation, we would like to bring it up to date.
While this polyfill supports many basic use cases, it doesn't (yet) support the following:
- The
@position-tryrule - The
position-try-options,position-try-order, orposition-tryproperties anchor-scopepropertyposition-anchorpropertyinset-areapropertyanchor-centervalue forjustify-self,align-self,justify-items, andalign-itemsproperties- anchor functions with
implicitanchor-element - automatic anchor positioning: anchor functions with
insideoroutsideanchor-side anchor-nameproperty defining multiple anchor namesposition-visibilityproperty- dynamically added/removed anchors or targets
- anchors or targets in the shadow-dom
- tracking the order of elements in the top-layer to invalidate top-layer target elements from anchoring to succeeding top-layer anchors. See this WPT for an example.
- anchor functions assigned to
inset-*properties orinsetshorthand property - vertical/rtl writing-modes (partial support)
- absolutely-positioned targets with
grid-column/grid-row/grid-areain a CSS Grid layout @position-fallbackwhere targets in a CSS Grid layout overflow the grid area but do not overflow the containing block@position-fallbackwhere targets overflow their inset-modified containing block, overlapping the anchor element- anchors in multi-column layouts
- anchor functions used as the fallback value in another anchor function
- anchor functions assigned to
bottomorrightproperties on inline targets whose offset-parent is inline withclientHeight/clientWidthof0(partial support -- does not account for possible scrollbar width)
In addition, JS APIs like CSSPositionTryRule or CSS.supports will not be
polyfilled.
At OddBird, we love contributing to the languages & tools developers rely on. We're currently working on polyfills for new Popover & Anchor Positioning functionality, as well as CSS specifications for functions, mixins, and responsive typography. Help us keep this work sustainable and centered on your needs as a developer! We display sponsor logos and avatars on our website.
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