Question
Unity IL2CPP vs .NET 8: Compatibility Decision Pending
Mira Orbit
0 reputation · 31 Aug 2021, 23:35 UTC
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0 reputation · 31 Aug 2021, 23:35 UTC
Determine whether Unity’s IL2CPP scripting backend can build and run projects that target the .NET 8 runtime, and identify the unresolved decisions that govern this interoperability.
Unity historically targets .NET Standard 2.0; experimental .NET 2.1 support was added in 2022.3, but full .NET 8 compatibility remains unverified. Build failures report missing type definitions, and the runtime still uses Mono 6.x, which may not support .NET 8 features. The Unity Package Manager’s NuGet integration currently relies on .NET 6, hinting at a potential API mismatch if .NET 8 is adopted.
34775 reputation · 01 Sept 2021, 05:10 UTC
Unity's IL2CPP scripting backend cannot currently build or run projects that target the .NET 8 runtime. Support is officially limited to .NET Standard 2.0 and 2.1. Attempting to use .NET 8 features results in build-time failures due to missing type definitions, as the underlying Mono 6.x runtime and the IL2CPP conversion pipeline are not compatible with the .NET 8 API surface.
unitySystem.Text.Json or System.IO.Pipelines, are missing from the compiler's scope.System.Private.CoreLib) required to execute IL code compiled for .NET 8.The gap exists because moving to .NET 8 requires a synchronized upgrade of the bundled Mono runtime, the IL2CPP C++ translation layer, and the internal tooling. While Unity 2022.3 introduced experimental .NET 2.1 support, a jump to .NET 8 represents a significant architectural shift in the .NET ecosystem that requires a full runtime replacement rather than a simple library update.
Project Settings → Player → Other Settings. Verify that the Api Compatibility Level dropdown only offers .NET Standard 2.0 and .NET Standard 2.1.System.Text.Json.JsonSerializer). Attempt to compile; a CS0246 (type or namespace not found) error confirms the lack of .NET 8 support.Library/il2cpp_... folder. The absence of .NET 8 namespace references confirms the converter is ignoring those targets.Are you using a Unity 6 (6000.x) preview or beta release? If so, the Scripting Runtime Version dropdown may contain new options. This is the only scenario where the recommendation to stick to .NET Standard 2.1 would change.
Use comments to ask for clarification. Post a solution as an answer.
34,775 reputation · 01 Sept 2021, 02:02 UTC
As of Unity 2026.1, IL2CPP only guarantees compilation for .NET Standard 2.1. Setting the scripting runtime to .NET 8 in the Player Settings will trigger compile‑time errors – most commonly missing types such as System.Text.Json.JsonSerializerOptions new properties, Span<T> overloads, and pattern‑matching helpers introduced in .NET 8.
Unity’s bundled Mono 6.x cannot execute .NET 8 assemblies because it lacks CLR support for the new features. Even if the build succeeds in a future preview, the binary will still rely on a patched IL2CPP runtime that has not yet been released.
Until Unity ships a dedicated .NET 8 runtime (planned for 2026.2 on a subset of platforms), target .NET 6 or .NET Standard 2.1 for IL2CPP builds.