UIDebuggingInformationOverlay

UIDebuggingInformationOverlay is a private UIWindow subclass created by Apple, presumably to help developers and designers debug Apple’s own iOS apps.

Harder to get at in iOS 11, but this post shows how to use swizzling to get it working there too.

Checking if we're running with a user gesture

function isUserInteraction() {
  const detectionElement = window.document.createElement('audio');
  detectionElement.play();
  return !detectionElement.paused;
}

The things I hate (and you should know) about Apple Universal Links

SampleViewer

A primitive viewer application for macOS 'sample'-files taken with the Sample command line tool or the Activity Viewer utility.