The problem everyone saw
Since Liquid Glass was introduced, readability criticism of the Mac interface has been among the most frequent in developer forums and public feedback. Very light or very dark backgrounds interfered with text readability in toolbars and windows, making the interface visually unstable in certain contexts.
The solution: a transparency slider
At WWDC 2026, Apple responded with a direct mechanism. According to the MacRumors live blog, the system now includes "a new slider to set the transparency from opaque to completely clear." CNBC confirmed that Apple made "significant improvements and optimizations to the design language to allow users to adjust transparency from fully clear to tinted, and improved text labels and toolbars so they are more adjustable."
Edge-to-edge sidebar and continuous refraction
Alongside the transparency slider, Apple modified sidebar behavior on macOS: sidebars now expand to the edge of the window, liquid glass refraction continues beneath the sidebar, and sidebar icons retain their color. The result is a more visually coherent interface where the Liquid Glass material does not interrupt its optical behavior at panel borders.
Why it's relevant
The distinction from the already-published slug ios-27-liquid-glass-slider-shortcut-linguaggio-naturale is that here the focus is on the macOS-specific implementation — with edge-to-edge sidebar and toolbar optimizations — not on language shortcuts or iPhone accessibility. On Mac, where screens are larger and usage contexts more varied, granular transparency control has a different practical impact.