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.

Important

The latest Unity 2021 release has a known blocking performance bug with HoloLens 2 if the project is using URP rendering pipeline.

For new projects using URP rendering, we recommend using latest Unity 2020.3.35f1 or later LTS with the latest Mixed Reality OpenXR plugin to avoid this issue.

If using other Unity releases, consult the known active blocking issues to ensure you avoid builds with other blocking issues.

Active blocking issues

Blocking issues	Status & Last Update	Versions with issue	Mitigation
ARM32 UWP Unity apps built in release mode using Visual Studio 2022 will hit an internal compiler error in Visual Studio.	Pending release: 2022/06/27	Visual Studio 2022 version 17.1.1+	Use Visual Studio 2019 or 2022 version <= 17.0
HL2 app using URP, WindowsXR plugin and Gamma color space rendering has worse render performance in Unity 2020 or later.	Investigating: 2022/05/06	Unity 2020.*.* with URP 10.*.* and Windows XR Plugin 4.*.*	Upgrade to OpenXR Plugin instead of WindowsXR plugin
HL2 app using URP has worse render performance in Unity 2021 compared to Unity 2020.	Investigating: 2022/05/06	Unity 2021.*.* with URP 12.*.*	Either avoid URP in Unity 2021 or use URP in Unity 2020.LTS

Resolved blocking issues

Blocking issues	Status & Last Update	Versions with issue	Versions with fixes
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 or 1.7.0~1	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