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There might be a time when you want to detect whether an app is running in Xcode Previews or not.

At first, I expected something like a targetEnvironment() condition that allows us to detect between builds on physical devices and simulators.

#if targetEnvironment(simulator)
   // code for the simulator here
#elseif targetEnvironment(preview) ❌
   // code for Xcode Previews here
#else
   // code for real devices here
#endif

Sadly, Swift doesn't provide such a condition for detecting the Xcode Previews environment.

But we still got some luck. Apple includes a process environment value that tells whether an app is running in the Xcode Previews environment .

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Detecting if a SwiftUI app is in Xcode Previews

ProcessInfo.processInfo.environment["XCODE_RUNNING_FOR_PREVIEWS"]

var isPreview: Bool {
    return ProcessInfo.processInfo.environment["XCODE_RUNNING_FOR_PREVIEWS"] == "1"
}

struct ContentView: View {
    var body: some View {
        VStack {
            Image(systemName: "globe")
                .imageScale(.large)
                .foregroundColor(.accentColor)
            Text("Hello, world!")
            if isPreview {
                // 1
                Text("In Preview")
            }
        }
        .padding()
    }
}

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