/ios-26-platform

Backward Compatibility

iOS 17/18 + iOS 26

UIDesignRequiresCompatibility Key

Opt Out of Liquid Glass (Temporarily)

<!-- Info.plist -->
<key>UIDesignRequiresCompatibility</key>
<true/>

Effect:

• App built with iOS 26 SDK
• Appearance matches iOS 18 and earlier
• Liquid Glass effects disabled
• Previous blur/material styles used

Migration Strategy

1. Ship with UIDesignRequiresCompatibility enabled
2. Audit interface changes in separate build
3. Update interface incrementally
4. Remove key when ready for Liquid Glass

@available Patterns

Basic Check

if #available(iOS 26, *) {
    content
        .glassEffect()
} else {
    content
        .background(.ultraThinMaterial)
}

View Modifier Pattern

extension View {
    @ViewBuilder
    func adaptiveGlass() -> some View {
        if #available(iOS 26, *) {
            self.glassEffect()
        } else {
            self.background(.regularMaterial)
        }
    }
}

// Usage
Button("Action") { }
    .adaptiveGlass()

Toolbar Spacer Fallback

extension View {
    @ViewBuilder
    func adaptiveToolbar() -> some View {
        if #available(iOS 26, *) {
            self.toolbar {
                ToolbarItemGroup(placement: .topBarTrailing) {
                    Button("Up") { }
                    Button("Down") { }
                    Spacer(.fixed) // iOS 26 feature
                    Button("Settings") { }
                }
            }
        } else {
            self.toolbar {
                ToolbarItem(placement: .topBarTrailing) {
                    Button("Up") { }
                }
                ToolbarItem(placement: .topBarTrailing) {
                    Button("Down") { }
                }
                ToolbarItem(placement: .topBarTrailing) {
                    Button("Settings") { }
                }
            }
        }
    }
}

WebView Fallback

struct ArticleView: View {
    let url: URL

    var body: some View {
        if #available(iOS 26, *) {
            WebView(url: url)
        } else {
            WebViewRepresentable(url: url) // UIViewRepresentable wrapper
        }
    }
}

// iOS 17/18 fallback
struct WebViewRepresentable: UIViewRepresentable {
    let url: URL

    func makeUIView(context: Context) -> WKWebView {
        WKWebView()
    }

    func updateUIView(_ webView: WKWebView, context: Context) {
        webView.load(URLRequest(url: url))
    }
}

@Animatable Fallback

#if swift(>=6.0)
@Animatable
struct ModernShape: Shape {
    var progress: Double

    @AnimatableIgnored
    var style: ShapeStyle
}
#else
struct LegacyShape: Shape {
    var progress: Double

    var animatableData: Double {
        get { progress }
        set { progress = newValue }
    }
}
#endif

Search Tab Role Fallback

TabView {
    if #available(iOS 26, *) {
        SearchView()
            .tabItem { Label("Search", systemImage: "magnifyingglass") }
            .tabRole(.search)
    } else {
        SearchView()
            .tabItem { Label("Search", systemImage: "magnifyingglass") }
    }
}

AttributedString TextEditor

struct CommentEditor: View {
    @State private var richText = AttributedString("Comment")
    @State private var plainText = "Comment"

    var body: some View {
        if #available(iOS 26, *) {
            TextEditor(text: $richText) // Rich text support
        } else {
            TextEditor(text: $plainText) // Plain text only
        }
    }
}

Migration from Previous Materials

From UIBlurEffect

// Before (UIKit)
let blurEffect = UIBlurEffect(style: .systemMaterial)
let blurView = UIVisualEffectView(effect: blurEffect)

// After (SwiftUI with fallback)
extension View {
    @ViewBuilder
    func adaptiveMaterial() -> some View {
        if #available(iOS 26, *) {
            self.glassEffect()
        } else {
            self.background(.regularMaterial)
        }
    }
}

From Custom Materials

Keep custom materials when:

• Backward compatibility with iOS < 26 required
• Specific artistic effect not achievable with glass
• Non-standard UI paradigm

Testing Checklist

iOS 26 Tests

• Liquid Glass appearance correct
• Scroll edge effects working
• Toolbar grouping renders properly
• Search placement is platform-appropriate
• Accessibility settings respected

iOS 17/18 Tests

• Fallback materials render correctly
• No runtime crashes from @available checks
• Functionality preserved without glass
• Layout doesn't break

Deprecated APIs

iPadOS 26

<!-- Remove entirely — deprecated in iPadOS 26 -->
<key>UIRequiresFullscreen</key>

Apps must support resizable windows on iPad.

SwiftUI Updates

// Old (deprecated)
.onChange(of: value, perform: { newValue in })

// New (iOS 17+)
.onChange(of: value) { oldValue, newValue in }

Performance Considerations

When supporting multiple iOS versions:

• Use @available checks at view level, not inside body
• Prefer conditional view modifiers over entire view branches
• Test performance on oldest supported version
• Profile with Instruments on both old and new iOS