Sadly enough, we discovered today that our web application was crashing when browsing in private mode on Safari (this happened during a product demo of our CEO ?). It was a bit unfortunate that we had to discover it like that and that none of us had tested it with Safari in private mode. However, we were not expecting that modern browsers would do such weirdness, even caniuse.com doesn't mention it. But still, we can't assume things like that of course.