This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The IntersectionObserver interface's read-only root property identifies the Element whose bounds are treated as the bounding box of the viewport for the element which is the observer's target. If the root is null, then the bounds of the actual document viewport are used.


var root = IntersectionObserver.root;


A Element object whose bounding box is used as the bounds of the viewport for the purposes of determining how much of the target element is visible. The intersection of this bounding rectangle, offset by any margins specified in the options passed to the IntersectionObserver() constructor, the target element's bounds, minus the bounds of every element or other object which overlaps the target element, is considered to be the visible area of the target element.

If root is null, then the bounds of the document's viewport (that is, the visible area of the document) are used as the root.


Specification Status Comment
Intersection Observer
The definition of 'IntersectionObserver' in that specification.
Working Draft Initial definition

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support5115


53 — 551

No ? ?
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support5151 Yes ? ? ?5.0

1. From version 53 until version 55 (exclusive): this feature is behind the dom.IntersectionObserver.enabled preference (needs to be set to true). To change preferences in Firefox, visit about:config.

Document Tags and Contributors

Contributors to this page: fscholz, Sheppy, UsainBloot, erikadoyle, ziyunfei, Sebastianz
Last updated by: fscholz,