Whether you watch Netflix on your iPhone, iPad, Mac, or Apple TV, the quality of the video—and whether it stutters or skips—is determined by the bandwidth of your Internet connection. Netflix recommends 25 megabits per second (Mbps) of download speed for Ultra HD quality, 5 Mbps for HD, and 3 Mbps for SD. Netflix says that 1.5 Mbps is the lowest recommendation for a broadband connection, 
and notes that 0.5 Mbps is the minimum required. So how do you tell what your real-world download speed is? Check Netflix’s new fast.com Web site, which is a quick and easy way to determine how much bandwidth you get. And if what you see doesn’t match with what you think you’re paying your Internet service provider for, call the ISP and make sure your connection is working properly.