Window: scrollY property

BaselineWidely available *

This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.

* Some parts of this feature may have varying levels of support.

The read-onlyscrollY property of theWindow interface returns the number of pixels by which the document is currently scrolled vertically. This value is subpixel precise in modern browsers, meaning that it isn't necessarily a whole number. You can get the number of pixels the document is scrolled horizontally from thescrollX property.

Value

A double-precision floating-point value indicating the number of pixels by which the document is currently scrolled vertically from the origin, where a positive value means the content is scrolled down (to reveal more content to the bottom). In more technical terms,scrollY returns the Y coordinate of the top edge of the currentviewport. If the document isn't scrolled at all top or down, thenscrollY is 0. If there is no viewport, the returned value is 0. If the document is rendered on a subpixel-precise device, then the returned value is also subpixel-precise and may contain a decimal component.

Note:If you need an integer value, you can useMath.round() to round it off.

Safari responds to overscrolling by updatingscrollY beyond the maximum scroll position (unless the default "bounce" effect is disabled, such as by settingoverscroll-behavior tonone), while Chrome and Firefox do not. For example,scrollY may be negative on Safari just by continuing to scroll up when the document is already at the top.

This property is read-only. To scroll the window to a particular place, useWindow.scroll().

Examples

// make sure and go down to the second pageif (window.scrollY) {  window.scroll(0, 0); // reset the scroll position to the top left of the document.}window.scrollByPages(1);

Notes

Use this property to check that the document hasn't already been scrolled when usingrelative scroll functions such asscrollBy(),scrollByLines(), orscrollByPages().

ThepageYOffset property is an alias for thescrollY property. This means if you haven't re-assigned either property,window.pageYOffset === window.scrollY is always true.