OP's Note: I've had this posted in the El Capitan forum for a few weeks with 200+ views, but no responses. I thought putting it here might attract an idea or two. Thanks. __________________________ I have a late-2013 iMac (pre-5K) that suddenly won't show embedded video in Safari, including YouTube videos. The problem is characterized by a black frame where the HTML5 player ought to be displayed. I can't swear to it, but I think this issue dates to the installation of 10.11.6. I do not have Flash installed. If I feel compelled to view a video I'll copy the link into a Chrome browser. That works, but I really, really don't want to use Chrome. As far as I can tell the problem is limited to HTML5 videos in Safari. I've looked at Safari preferences and have reconfigured some I thought might help, to no avail. There's nothing on Apple's Support site that addresses my concern. Your thoughts?