Hence, the real product may appear different on real devices than it appears on virtual emulators in many cases. It’s a well-known fact that virtual device emulators and simulators are very slow on many platforms (like Android). Main part of the development process requires adaptation of the application to different screen sizes and resolutions on different devices, just like the different screen sizes of iPhone 4/4S (3.5″), iPhone 5/5S (4″), iPhone 6S/7/8/SE (4.7″) and iPhone 7/8 Plus (5.5″). Click here for more information on online iOS and Android emulation and simulation on Windows and any other desktop OS