Created attachment 442364 [details] bug reproducing We have the bottom tabs bar on our website which is fixed positioned at the bottom. When the user starts scrolling to the top, safari bottom bar and smart app banner start appearing, but the safe bottom offsets are calculating wrong. On the attached videos you can see debug boxes where yellow is marks "position: fixed" behavior. When I enable the "Safe area margin" checkbox, it would add safe bottom offset to the margin. I've recorded both top and bottom bar positions which were introduced in iOS 15. https://m.vk.com/?act=_apple_viewport_bug
<rdar://problem/84692042>
The fix for this issue was needed outside the WebKit project, therefore this is being resolved as 'Moved'. This issue should be fixed now in iOS 15.4 Beta.