Confirmed on iOS 8.0 and up. Test page at http://bradfrost.com/demo/fixed/index.html STR: 1) Create a WKWebView, set its frame full screen and set its resizing mask to flexible width/height 2) Load http://bradfrost.com/demo/fixed/index.html 3) See the header and footer correctly positioned and have the width of the screen 4) Change device to landscape 5) See the header and footer still have the original width. Forcing a re-layout by scrolling a bit makes the header and footer widths update correctly. In Firefox for iOS we have a workaround for this issue where we nudge the scrollView a bit to force a layout. See https://github.com/mozilla/firefox-ios/commit/c93880e27c930d3f41cd8f44b1bcbd642ed6c81d#diff-6d1fb0cf203fcd3c299d4ba3f07f21deR130
<rdar://problem/21350212>