IntersectionObserverEntry.intersectionRatio

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

The IntersectionObserverEntry interface's read-only intersectionRatio property tells you how much of the target element is currently visible within the root's intersection ratio, as a value between 0.0 and 1.0.

Syntax

var intersectionRatio = IntersectionObserverEntry.intersectionRatio;

Value

A number between 0.0 and 1.0 which indicates how much of the target element is actually visible within the root's intersection rectangle. More precisely, this value is the ratio of the area of the intersection rectangle (intersectionRect) to the area of the target's bounds rectangle (boundingClientRect).

If the area of the target's bounds rectangle is zero, the returned value is 1 if isIntersecting is true or 0 if not.

Example

In this simple example, an intersection callback sets each target element's opacity to the intersection ratio of that element with the root.

function intersectionCallback(entries) {
  entries.forEach(function(entry) {
    entry.target.style.opacity = entry.intersectionRatio;
  });
}

To see a more concrete example, take a look at Handling intersection changes in Timing element visibility with the Intersection Observer API.

Specifications

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

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidiOS SafariSamsung Internet
Basic support
Experimental
Chrome Full support 51Edge Full support 15Firefox Full support 55
Full support 55
No support 53 — 55
Disabled
Disabled 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.
IE No support NoOpera ? Safari ? WebView Android Full support 51Chrome Android Full support 51Edge Mobile Full support YesFirefox Android ? Opera Android ? Safari iOS ? Samsung Internet Android Full support 5.0

Legend

Full support  
Full support
No support  
No support
Compatibility unknown  
Compatibility unknown
Experimental. Expect behavior to change in the future.
Experimental. Expect behavior to change in the future.
User must explicitly enable this feature.
User must explicitly enable this feature.

Document Tags and Contributors

Contributors to this page: tschwartz, fscholz, Sheppy
Last updated by: tschwartz,