Scripting Runtime Upgrade

For 2017.1 the option to use .NET 4.6 will be an experimental, per project option. This option is in the GUI as a Player Setting above Scripting BackendA framework that powers scripting in Unity. Unity supports three different scripting backends depending on target platform: Mono, .NET and IL2CPP. Universal Windows Platform, however, supports only two: .NET and IL2CPP. More info
See in Glossary and Api Compatibility Level:

The equivalent scripting API is the PlayerSettings.scriptingRuntimeVersion property. Note that changing this setting requires an Editor restart since it affects the Editor as well as players.

By default nothing should change about how Unity behaves or what .NET functionality is available. Once you opt-in to the new .NET 4.6 for a project, you will be able to use C# 6, .NET 4.6 class libraries, and new runtime features in user scriptsA piece of code that allows you to create your own Components, trigger game events, modify Component properties over time and respond to user input in any way you like. More info
See in Glossary and precompiled assemblies.

FAQ

What platforms does this affect?

All of them, but in different ways:

• Editor and Standalone use the new version of Mono when this option is enabled.

• All console platforms will only be able to use IL2CPPA Unity-developed scripting back-end which you can use as an alternative to Mono when building Projects for some platforms. More info
  See in Glossary when targeting the new .NET version.

• iOSApple’s mobile operating system. More info
  See in Glossary and WebGLA JavaScript API that renders 2D and 3D graphics in a web browser. The Unity WebGL build option allows Unity to publish content as JavaScript programs which use HTML5 technologies and the WebGL rendering API to run Unity content in a web browser. More info
  See in Glossary will continue to be IL2CPP only.

• Android will continue to support both Mono and IL2CPP.

• Other platforms are still undergoing work to support either new Mono or IL2CPP

At the current time (2017.1b4) please focus on using this option on desktop, iOS, and Android. Support for other platforms is still under development.

What about IL2CPP?

IL2CPP fully supports the new .NET 4.6 APIs and features.

How stable is the updated Mono/IL2CPP?

The internal, automated tests for Unity pass with the new Mono/IL2CPP. Of course, we still expect you may encounter issues. Please file bugs for any issues you encounter.

Does this preview include a new GC?

No. This is an upgrade of the class libraries and runtime, but we are still using the Boehm GC. We are targeting a new version of Boehm that we use with IL2CPP (so IL2CPP and Mono will have exact same GC).

Wait, why don’t we have a new GC?

The newer Mono garbage collector (SGen) requires additional work in Unity and will follow once we have stabilized the new runtime and class libraries.

Can I debug managed code with this new Mono?

VSTU 3.1 is required for our new Mono. Please install it to use the new Mono runtime on Windows.

Why are my builds larger with the new .NET version?

The .NET 4.6 class libraries are quite larger than our current .NET 3.5 class libraries. We are actively working on improving the managed linker to reduce size further.

Additionally, we are working on a new Unity specific class library API profile (like our current unity profile) that will

a) be specifically implemented to work on AOT platforms

b) smaller in surface area and internally designed to be strippable/linkable

c) support netstandard 2.0 (yet to be officially released)

When I try this new option, something doesn’t work. What should I do?

Please file a bug. We will be rapidly fixing them!

---

• 2018–03–19 Page published with no editorial review

• New feature in Unity 2017.1 NewIn20171

• MonoDevelop replaced by Visual Studio from 2018.1