pageshow event should be dispatched asynchronously see step #4.5 of the history traversal algorithm (section 6.5.9): http://www.whatwg.org/specs/web-apps/current-work/multipage/history.html#traverse-the-history this is (probably) a recent change to the spec Found when exploring fixing https://bugs.webkit.org/show_bug.cgi?id=36201 and https://bugs.webkit.org/show_bug.cgi?id=36202
<rdar://problem/7769669>
Would there be an observable difference?
You could probably observe this on an iframe in the same origin.