diff --git a/Sources/Adwaita/Model/User Interface/App/App.swift b/Sources/Adwaita/Model/User Interface/App/App.swift
index 61077e8..7528846 100644
--- a/Sources/Adwaita/Model/User Interface/App/App.swift	
+++ b/Sources/Adwaita/Model/User Interface/App/App.swift	
@@ -24,7 +24,8 @@
 public protocol App {
 
     /// The app's application ID.
-    var id: String { get }
+    static var id: String { get }
+
     /// The app's windows.
     @SceneBuilder var scene: Scene { get }
     // swiftlint:disable implicitly_unwrapped_optional
@@ -39,8 +40,12 @@ public protocol App {
 
 extension App {
 
+    @available(*, deprecated, message: "The 'id' property is removed. Please use the new static id instead.")
+    var id: String { Self.id }
+
     /// The application's entry point.
     public static func main() {
+        GTUIApp.appID = Self.id
         let app = setupApp()
         app.run()
     }
@@ -50,7 +55,7 @@ extension App {
     /// To run the app, call the ``GTUIApp/run(automaticSetup:manualSetup:)`` function.
     public static func setupApp() -> GTUIApp {
         var appInstance = self.init()
-        appInstance.app = GTUIApp(appInstance.id) { appInstance }
+        appInstance.app = GTUIApp(Self.id) { appInstance }
         GTUIApp.updateHandlers.append { force in
             var removeIndices: [Int] = []
             for (index, window) in appInstance.app.sceneStorage.enumerated() {
@@ -64,7 +69,6 @@ extension App {
                 appInstance.app.sceneStorage.remove(at: index)
             }
         }
-        GTUIApp.appID = appInstance.id
         return appInstance.app
     }
 
diff --git a/Sources/Adwaita/Model/User Interface/App/GTUIApp.swift b/Sources/Adwaita/Model/User Interface/App/GTUIApp.swift
index 3fc9530..5ae3c10 100644
--- a/Sources/Adwaita/Model/User Interface/App/GTUIApp.swift	
+++ b/Sources/Adwaita/Model/User Interface/App/GTUIApp.swift	
@@ -13,8 +13,7 @@ public class GTUIApp {
     /// The handlers which are called when a state changes.
     static var updateHandlers: [(Bool) -> Void] = []
     /// The app's id for the file name for storing the data.
-    static var appID = "temporary"
-
+    static var appID: String!
     /// The pointer to the application.
     public var pointer: UnsafeMutablePointer<GtkApplication>?
     /// Fields for additional information.