IntersectionObserverEntry: intersectionRatio property

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since March 2019.

The intersectionRatio read-only property of the IntersectionObserverEntry interface 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.

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.

Examples

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

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

To see a more concrete example, take a look at Handling intersection changes.

Specifications

Specification

Intersection Observer
# dom-intersectionobserverentry-intersectionratio

Browser compatibility

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Intersection Observer API
IntersectionObserverEntry
Constructor
1. IntersectionObserverEntry()
Instance properties
Related pages for Intersection Observer API
1. IntersectionObserver
Guides
1. Timing element visibility with the Intersection Observer API