We've updated the spec so that only one share() can occur at the same time: https://github.com/w3c/web-share/pull/113 Right now, if two calls to .share() are made in Safari, both shares reject. We've added a Web Platform Test also: https://github.com/web-platform-tests/wpt/pull/18486
<rdar://problem/55227424>
Looks like this got fixed by: https://bugs.webkit.org/show_bug.cgi?id=229132 It checks m_hasPendingShare.