The displays on both the iPhone 12 Pro and iPhone 12 Pro Max will offer a 120Hz refresh rate, according to Ice Universe. This person regularly leaks news related to Samsung devices, but they say that this iPhone 12 info came to them from a "reliable source".
Apple already offers 120Hz refresh rate support on its iPad Pro. The company calls this feature ProMotion, and it's been available on the iPad Pro models since the 10.5-inch and 12.9-inch models that launched in 2017.
However, every iPhone model released to date has been stuck at 60Hz. It's possible that Apple has been trying to figure out how to bring a high refresh rate to the iPhone without having it drain the battery too heavily. Rumors have said that the iPhone 12 Pro and Pro Max batteries could be as large as 4400mAh, which would be much bigger than 3046mAh and 3969mAh batteries found in the iPhone 11 Pro and Pro Max, and that would also help to combat the battery drain that a 120Hz display would cause.
Reports have also said that the iPhone 12 Pro and Pro Max will have 6.1-inch and 6.7-inch screens. Both would be bigger than the iPhone 11 Pro and Pro Max, which have 5.8-inch and 6.5-inch displays, respectively.
A reliable source, if there is no accident, iPhone 12 Pro and iPhone 12 Pro Max have basically determined the maximum 120Hz refresh rate.
— Ice universe (@UniverseIce) June 26, 2020