Looking at the home screens, the primary difference you'll find is that in iOS 26 the background of the dock and the search option that sits in between the dock and the home screen icons are more transparent and have a sheen to the edges, whereas in iOS 18, these are slightly darker.

Apple apparently wasn’t satisfied with the Liquid Glass look in beta 2. iOS 26 beta 3 introduces another change, and now the glass isn’t that liquid anymore. The transparency has been reduced even further, giving the overall effect of frosted glass.

The early version in the first developer beta of iOS 26 and the accompanying updates for Apple's other devices still left room for improvement in terms of usability, accessibility, and legibility.