iOS 26/27 Liquid Glass — design rules + the SwiftUI APIs that ship it

Liquid Glass is the unified material introduced across iOS/iPadOS/macOS Tahoe/watchOS/tvOS 26 (WWDC June 2025) and refined as Liquid Glass v2 at WWDC26 (June 8–12 2026) shipping in iOS/iPadOS/macOS 27. iOS 26 is the now-shipping baseline; iOS 27 (the WWDC26 cycle) is the current announced iteration — Liquid Glass v2 is the latest material, not the original WWDC25 one. Sources below are anchored to Apple primary material — WWDC25 session 219 "Meet Liquid Glass" and session 323 "Build a SwiftUI app with the new design", plus the WWDC26 keynote + "What's new in SwiftUI" coverage — and confirmed developer.apple.com/documentation symbol pages. API symbols are marked ✅ (shown in an Apple source) or ⚠️ (community-reported only — verify in the Xcode 26/27 SDK before relying on it). Do not treat ⚠️ items as canonical. (Stamp: June 2026.)

Source: WWDC25 sessions 219 + 323; WWDC26 keynote (June 8 2026) "Liquid Glass improvements"; WWDC26 "What's new in SwiftUI"; developer.apple.com/documentation. WWDC26 specifics cross-checked against MacRumors (2026-06-08) + DEV/arshtechpro WWDC26 SwiftUI breakdown — Apple dev pages render in JS, so secondary tech sources used to confirm.

1. The one mental model that prevents 90% of mistakes

Glass is the functional/navigation layer that floats above the content layer. Content scrolls underneath it.

• Apple, verbatim: "Liquid Glass is best reserved for the navigation layer that floats above the content of your app." (219)
• "making [a tableview] Liquid Glass would make it compete with other elements and muddy the hierarchy. So keep it in the content layer instead." (219)
• It is a light-bending meta-material, not a blur — its signature cue is lensing (it bends/concentrates light so content shows through while staying separated). It materializes in/out (modulating lensing), it doesn't fade. (219)
• It is continuously adaptive: each layer adapts to what's behind it. Small chrome (nav/tab bars) flips light↔dark with the background; large elements (sidebars, menus) adapt tint but do not flip (flipping would distract). (219)