Debug your app with Apple's private UIDebuggingInformationOverlay. Supports iOS 13-17+.

DebuggingOverlay.swift

import UIKit
import ObjectiveC.runtime

/// An enum that displays UIKitCore's `UIDebuggingInformationOverlay`.
enum DebuggingOverlay {

    /// Shows the `UIDebuggingInformationOverlay`.
    @available(iOS 13, *)
    static func show() {
        struct Once {
            /// Replace the overlay's init method with UIWindow's.
            static let run: Void = {
                let initSelector = NSSelectorFromString("init")
                let debugOverlayClass = NSClassFromString("UIDebuggingInformationOverlay") as? UIWindow.Type
                guard let newInitMethod = class_getInstanceMethod(UIWindow.self, initSelector) else {
                    fatalError("UIWindow.init was nil")
                }
                let newImplementation = method_getImplementation(newInitMethod)
                class_replaceMethod(debugOverlayClass, initSelector, newImplementation, nil)
            }()
        }
        Once.run

        // `UIDebuggingInformationOverlay.prepareDebuggingOverlay()` calls the _UIGetDebuggingOverlayEnabled
        // which checks if the device is internal to Apple. Bypass the check by invoking a tap
        // gesture.
        let tapGesture = UITapGestureRecognizer()
        tapGesture.state = .ended

        let handlerClass = NSClassFromString("UIDebuggingInformationOverlayInvokeGestureHandler") as! NSObject.Type
        let handler = handlerClass.perform(NSSelectorFromString("mainHandler")).takeUnretainedValue()
        let _ = handler.perform(NSSelectorFromString("_handleActivationGesture:"), with: tapGesture)

        // If the app supports multiple scenes the debug menu needs to be added as a subview.
        guard
            Bundle.main.object(forInfoDictionaryKey: "UIApplicationSceneManifest") != nil,
            let debugOverlayClass = NSClassFromString("UIDebuggingInformationOverlay") as? UIWindow.Type,
            let debugOverlayView = debugOverlayClass.perform(NSSelectorFromString("overlay")).takeUnretainedValue() as? UIView,
            let keyWindow = getKeyWindow()
        else {
            return
        }

        debugOverlayView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
        keyWindow.addSubview(debugOverlayView)
    }
    
    /// Returns the app's key window.
    private static func getKeyWindow() -> UIWindow? {
        UIApplication.shared.connectedScenes
            .flatMap { ($0 as? UIWindowScene)?.windows ?? [] }
            .last { $0.isKeyWindow }
    }
}