After Craig Feherighi demoed the iPhone X for the first time at last month's keynote, it became evident that several changes to the iOS user interface would need to accommodate for the new edge-to-edge OLED display, its rounded corners, and the notch.
One of the differences was in the App Switcher where each of the cards exhibits heavily-rounded corners that match the aesthetic of the device's display. Other iPhone models don’t have as pronounced of roundness, but a new free jailbreak tweak called switcherRadii by iOS developer CreatureSurvive can replicate this effect on your non-X handset.