FullscreenGameView.cs

#if UNITY_EDITOR

using System;
using System.Reflection;
using UnityEditor;
using UnityEngine;

/// <summary>
/// Little utility for opening a "Game" view in fullscreen. Will be opened on whatever Unity thinks is the "main"
/// monitor at the moment. The hotkey will toggle the window; however, if for some reason this breaks, fullscreen
/// windows can be closed via Alt+F4 as long as the editor is not in play mode.
/// </summary>
/// <remarks>
/// Confirmed to work in Unity 2019 and 2020. May work in earlier and later versions. No promises.
/// </remarks>
public static class FullscreenGameView
{
    static readonly Type GameViewType = Type.GetType("UnityEditor.GameView,UnityEditor");
    static readonly PropertyInfo ShowToolbarProperty = GameViewType.GetProperty("showToolbar", BindingFlags.Instance | BindingFlags.NonPublic);
    static readonly object False = false; // Only box once. This is a matter of principle.

    static EditorWindow instance;

    [MenuItem("Window/General/Game (Fullscreen) %#&2", priority = 2)]
    public static void Toggle()
    {
        if (GameViewType == null)
        {
            Debug.LogError("GameView type not found.");
            return;
        }

        if (ShowToolbarProperty == null)
        {
            Debug.LogWarning("GameView.showToolbar property not found.");
        }

        if (instance != null)
        {
            instance.Close();
            instance = null;
        }
        else
        {
            instance = (EditorWindow) ScriptableObject.CreateInstance(GameViewType);

            ShowToolbarProperty?.SetValue(instance, False);

            var desktopResolution = new Vector2(Screen.currentResolution.width, Screen.currentResolution.height);
            var fullscreenRect = new Rect(Vector2.zero, desktopResolution);
            instance.ShowPopup();
            instance.position = fullscreenRect;
            instance.Focus();
        }
    }
}

#endif

Before using this

• Make sure to set the game window to the same aspect ratio as your screen or this will break your rendering
  
• And also open the window after entering play mode or this will break your window layout.

Works perfectly, thanks!

Thanks so much for this! However, closing the window doesn't usually work this way for me, so I found it useful to also add another MenuItem shortcut that changes the layout back to normal. Something like this:

[MenuItem("Window/LayoutShortcuts/Default %q", false, 2)]
static void DefaultLayout()
{
    EditorApplication.ExecuteMenuItem("Window/Layouts/Default");
}

(Based on https://answers.unity.com/questions/23668/editor-layout-hotkeys.html)

Thanks a lot, this was the only solution that worked for me on my Linux. Improved it a bit to fit for my purposes:
https://gist.github.com/Chillu1/4c209308dc81104776718b1735c639f7

Awesome dude! Works perfectly. I've needed it to record my VR application gameplay (before building it) with the highest resollution possible. Thank You!

for other users

using ctrl+shift+alt+F as shortcutkey

watch this youtube video for more info: https://youtu.be/ebRRYUawPZk

#if UNITY_EDITOR

using System;
using System.Reflection;
using UnityEditor;
using UnityEngine;

/// <summary>
/// Little utility for opening a "Game" view in fullscreen. Will be opened on whatever Unity thinks is the "main"
/// monitor at the moment. The hotkey will toggle the window; however, if for some reason this breaks, fullscreen
/// windows can be closed via Alt+F4 as long as the editor is not in play mode.
/// </summary>
/// <remarks>
/// Confirmed to work in Unity 2019 and 2020. May work in earlier and later versions. No promises.
/// </remarks>
public static class FullscreenGameView
{
    static readonly Type GameViewType = Type.GetType("UnityEditor.GameView,UnityEditor");
    static readonly PropertyInfo ShowToolbarProperty = GameViewType.GetProperty("showToolbar", BindingFlags.Instance | BindingFlags.NonPublic);
    static readonly object False = false; // Only box once. This is a matter of principle.

    static EditorWindow instance;

    [MenuItem("Window/General/Game (Fullscreen) %#&f", priority = 2)]
    public static void Toggle()
    {
        if (GameViewType == null)
        {
            Debug.LogError("GameView type not found.");
            return;
        }

        if (ShowToolbarProperty == null)
        {
            Debug.LogWarning("GameView.showToolbar property not found.");
        }

        if (instance != null)
        {
            instance.Close();
            instance = null;
        }
        else
        {
            instance = (EditorWindow)ScriptableObject.CreateInstance(GameViewType);

            ShowToolbarProperty?.SetValue(instance, False);

            var desktopResolution = new Vector2(Screen.currentResolution.width, Screen.currentResolution.height);
            var fullscreenRect = new Rect(Vector2.zero, desktopResolution);
            instance.ShowPopup();
            instance.position = fullscreenRect;
            instance.Focus();
        }
    }
}

#endif