A convention that changes
Since the original iPhone, notifications have always arrived from the top of the screen. iOS 27 breaks that convention: banners slide in from the left edge, a detail MacRumors had previewed citing Bloomberg before the keynote and which was confirmed in the system update announced at WWDC.
Why from the left
Apple offered no explicit explanation during the presentation. A plausible reading is that the top edge is increasingly occupied by the Dynamic Island and status indicators, and a lateral slide-in reduces visual overlap with ongoing content — videos, maps, games. The swipe-right-to-dismiss gesture remains consistent with the new direction of arrival.
Small friction, big habit to relearn
This is not a functional change, but it is the kind of modification that generates friction in the first days of use. The muscle memory of glancing to the top-left for incoming notifications is more than a decade old. The choice makes sense from a design standpoint, but the adjustment will be noticeable.