Application.Unload

Description

Unloads the Unity runtime.

Unload the Unity runtime. Similar to quitting but the application process does not exit. This is useful when using Unity as a component in another application. For example, if you use Unity to display some special content but do not want to keep the Unity engine resident in memory when it is not needed. IMPORTANT: Only supported on iOS and Windows Store. IMPORTANT: This function does not return.

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour {
    void Update() {
        if (Input.GetKey("escape"))
            Application.Unload();
        
    }
}