Bug in iOS 9.3 lets you make folder icons circular – here's how to take advantage of it30
The bugger was found in iOS 9.3 and 9.3.1 and occurs when you choose to do something most users will probably never think of in their lives – which is set up a 3x3 pixel wallpaper. That's literally it – no additional modding is required to round out your folders.
Check out the slideshow for the instructions and the hearty selection of colorful 3x3 pixel wallpapers that you can download on your iOS device and make it do the magic trick. Just keep in mind that rounded folders won't work if you have turned on the "Reduce translucency" setting inside the Accessibility settings menu.