Known issues in Unity versions and packages

Some versions of Unity or Unity plugins have known incompatibilities blocking apps from working as expected on HoloLens 2 or Windows Mixed Reality devices. While we generally support all LTS versions of Unity and their verified plugins, we recommend avoiding those specific builds of Unity and Unity plugins to ensure your apps work as expected.

We recommend that you use the latest patch version of 2021.3 LTS and their recommended version of Unity plugins, together with the latest Mixed Reality OpenXR plugin.

If using an earlier Unity patch release, be sure to consult the known blocking issues table to ensure that you avoid builds with other blocking issues.

Active blocking issues

Blocking issues	Status & Last Update	Versions with issue	Mitigation
HL2 app using URP has worse render performance in Unity 2022 compared to Unity 2021 when using the default URP Lit material.	Investigating: 2023/01/04	Unity 2022.*.* with URP 13.*.*	Either avoid URP in Unity 2022, avoid using the default URP materials or use URP in Unity 2021.3.14+
Unable to build UWP app packages (APPX or MSIX) in Unity 2021 and 2022	In Progress: 2023/09/29	Reproducible with: 2021.3.30f1, 2022.3.8f1	Use Unity 2021.3.27 or earlier. Or manually add Appx Manifest to the app's VS project. See Unity's forum and Unity's Issue Tracker for more details.
An HL2 app importing both MRTK3 and Azure Spatial Anchors may present 'Guid for asset conflicts with' errors when the ARFoundation package version doesn't match the imported ARSubsystems version.			When using ARFoundation 5.x+, manually add com.unity.xr.arsubsystems version 5.0.2 to the project's Package Manager. You'll get a warning that ARSubsystems has been deprecated, but it can be ignored.

Resolved blocking issues

Blocking issues	Status & Last Update	Versions with issue	Versions with fixes
HL2 app crashes when hands are detected.	Fixed: 2023/03/24	Unity 2022, Unity 2021, Unity 2020 with com.unity.inputsystem 1.5.0	Use com.unity.inputsystem 1.5.1 or later
HL2 app using URP has worse render performance in Unity 2021 compared to Unity 2020.	Fixed: 2023/01/13	Unity version < 2021.3.14f1 with URP 12.*.*	Use Unity 2021.3.14f1 and later
Building application via IL2CPP in Unity fails due to compilation errors. For more information on the root cause, refer to the discussion here.	Fixed: 2022/11/10	Visual Studio 2022 version 17.4+ with Unity versions < 2020.3.42f1, 2021.3.14f1, 2022.1.23f1, 2022.2.0b16 and 2023.1.0a19	Use Visual Studio 2019 or Unity version >= 2020.3.42f1, 2021.3.14f1, 2022.1.23f1, 2022.2.0b16 or 2023.1.0a19
Holographic App Remoting remoting app using Unity's OpenXR plugin 1.5.1 fails to connect to remoting player if the hosting PC doesn't have other VR headsets attached.	Fixed: 2022/10/04	Unity 2020 or Unity 2021 with Unity OpenXR plugin = 1.5.0, 1.5.1 and 1.5.2	If using Holographic App Remoting, use Unity OpenXR plugin <= 1.4.3 or >= 1.5.3
ARM32 UWP Unity apps built in release mode using Visual Studio 2022 will hit an internal compiler error in Visual Studio.	Fixed: 2022/08/09	Visual Studio 2022 version 17.1.1+	Use Visual Studio 2019 or Visual Studio 2022 version >= 17.3.*
HL2 app using URP, WindowsXR plugin and Gamma color space rendering has worse render performance in Unity 2020 or later.	Fixed: 2022/06/15	Unity 2020.*.* with URP 10.*.* and Windows XR Plugin <=4.6.3	Use Windows XR Plugin version >= 4.6.4
HL2 app using Unity's Burst package (e.g. commonly used when using URP) will hit ILCPP compile error in VisualStudio.	Fixed: 2022/06/06	Unity Burst package 1.6.5, 1.7.0 or 1.7.1	Use Unity Burst package 1.6.6 or 1.7.2 or later versions.
Application with default splash screen will show four spinning dots when launching on HL2, or after the application is suspended and resumed.	Fixed: 2022/05/20	Unity 2020.3.32-34f1  and Unity 2021.2.17~19f1 and Unity 2021.3.0~3f1	Use Unity 2020.3.35f1 or Unity 2021.3.4f1 or later
HL2 application shows severely jittery image.	Fixed: 2021/12/02	Unity 2020.3.21f1 to Unity 2020.3.23f1	Use Unity 2020.3.24f1 and later
OpenXR backend with URP can deadlock on HL2.	Fixed: 2021/05/13	Unity 2020.3.0f1 to Unity 2020.3.7f1	Use Unity 2020.3.8f1 and later