VisualViewport
The VisualViewport
interface of the Visual Viewport API represents the visual viewport for a given window. For a page containing iframes, each iframe, as well as the containing page, will have a unique window object. Each window on a page will have a unique VisualViewport
representing the properties associated with that window.
You can get a window's visual viewport using Window.visualViewport
.
Note: Only the top-level window has a visual viewport that's distinct from the layout viewport. Therefore, it's generally only the VisualViewport
object of the top-level window that's useful. For an <iframe>
, visual viewport metrics like VisualViewport.width
always correspond to layout viewport metrics like document.documentElement.clientWidth
.
Instance properties
VisualViewport
also inherits properties from its parent, EventTarget
.
VisualViewport.offsetLeft
Read only-
Returns the offset of the left edge of the visual viewport from the left edge of the layout viewport in CSS pixels.
VisualViewport.offsetTop
Read only-
Returns the offset of the top edge of the visual viewport from the top edge of the layout viewport in CSS pixels.
VisualViewport.pageLeft
Read only-
Returns the x coordinate of the visual viewport relative to the initial containing block origin of the top edge in CSS pixels.
VisualViewport.pageTop
Read only-
Returns the y coordinate of the visual viewport relative to the initial containing block origin of the top edge in CSS pixels.
VisualViewport.width
Read only-
Returns the width of the visual viewport in CSS pixels.
VisualViewport.height
Read only-
Returns the height of the visual viewport in CSS pixels.
VisualViewport.scale
Read only-
Returns the pinch-zoom scaling factor applied to the visual viewport.
Events
Listen to these events using addEventListener()
or by assigning an event listener to the relevant oneventname
property of this interface.
Examples
Hiding an overlaid box on zoom
This example, taken from the Visual Viewport README, shows how to write a simple bit of code that will hide an overlaid box (which might contain an advert, say) when the user zooms in. This is a nice way to improve the user experience when zooming in on pages. A live sample is also available.
js
const bottomBar = document.getElementById("bottombar");
const viewport = window.visualViewport;
function resizeHandler() {
bottomBar.style.display = viewport.scale > 1.3 ? "none" : "block";
}
window.visualViewport.addEventListener("resize", resizeHandler);
Simulating position: device-fixed
This example, also taken from the Visual Viewport README, shows how to use this API to simulate position: device-fixed
, which fixes elements to the visual viewport. A live sample is also available.
js
const bottomBar = document.getElementById("bottombar");
const viewport = window.visualViewport;
function viewportHandler() {
const layoutViewport = document.getElementById("layoutViewport");
// Since the bar is position: fixed we need to offset it by the visual
// viewport's offset from the layout viewport origin.
const offsetLeft = viewport.offsetLeft;
const offsetTop =
viewport.height -
layoutViewport.getBoundingClientRect().height +
viewport.offsetTop;
// You could also do this by setting style.left and style.top if you
// use width: 100% instead.
bottomBar.style.transform = `translate(${offsetLeft}px, ${offsetTop}px) scale(${
1 / viewport.scale
})`;
}
window.visualViewport.addEventListener("scroll", viewportHandler);
window.visualViewport.addEventListener("resize", viewportHandler);
Note: This technique should be used with care; emulating position: device-fixed
in this way can result in the fixed element flickering during scrolling.
Specifications
Specification |
---|
CSSOM View Module # the-visualviewport-interface |
Browser compatibility
BCD tables only load in the browser
See also
- Web Viewports Explainer — useful explanation of web viewports concepts, including the difference between visual viewport and layout viewport.