Steps to reproduce: - Attach the iPhone or iPad to your Mac and inspect the current tab - Navigate this tab to: https://smartslider3.com/bugs/webkit/wrongheight/ - Examine the console - values are: el, jQuery->outerHeight(), jQuery->height(), el.getBoundingClientRect(), el.clientHeight, el.scrollHeight All height value should be 800 and width in getBoundingClientRect() should be 1440 What went wrong? At first load the browser reports wrong values. on my iPhone 11 it reports 1065px for the height and 414px for the width. Debugger stopped right after the console log. If you use the console in this paused state and try to print out values for the very same element, it will report the right values. Note: This only happens on the first load. Clear the whole cache to reproduce it again. Or enter private mode, open the page, to refresh close the tab and open a new tab. Happens on IOS 13.5, and IOS 12.9