A foldable display device may have housing portions coupled by a hinge. A flexible display may overlap the hinge. The hinge may have portions that rotate relative to each other about rotational axes that lie above the hinge to help reduce stress to the display. The hinge may have gear plates with interlocked teeth that synchronize rotational movement between left and right halves of the hinge. The hinge may also have asymmetric friction clips that impose different amounts of rotational friction to the hinge depending on the direction of rotation of the hinge.