Can .NET Framework and modern .NET applications be run side by side on the same machine, and how does that work?

Intermediate

Answer

Yes -- .NET Framework is a Windows OS component installed machine-wide with only one active version at a time (though it maintains backward compatibility across 4.x versions), while modern .NET installs side-by-side, allowing multiple independent versions (e.g., 6.0, 8.0, 9.0) to coexist without conflict since each app can reference its exact required runtime version explicitly.

# A machine can have all of these installed simultaneously without conflict:
# .NET Framework 4.8 (one version, machine-wide)
# .NET 6.0.25 runtime
# .NET 8.0.1 runtime
# Each app uses exactly the version it targets

Real-world example A Windows server hosts a legacy Framework 4.8 WCF service alongside a newer .NET 8 microservice simultaneously, with no version conflicts since modern .NET's side-by-side model isolates each application's runtime dependency.

Common follow-ups: How does an app pin its exact required runtime version at startup?;What happens if the required version isn't installed?

CLR & Runtime;.NET CLI SDK & Project Structure (csproj)

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