Runtime-specific apps no longer self-contained

Runtime-specific apps, or .NET apps with a RuntimeIdentifier, are no longer self-contained by default. Instead, they are framework-dependent by default.

This is a breaking change in the following situations:

• If you deployed, distributed, or published your app and didn't explicitly add the SelfContained property, but also didn't require that the .NET runtime be installed on the machine for it to work. In this case, you may have relied on the previous behavior to produce a self-contained app by default.
• If you rely on the IL Link tool. In this case, take the steps described under Recommended action to use IL Link again.

Previously, if a runtime identifier (RID) was specified (via RuntimeIdentifier), the app was published as self-contained, even if SelfContained wasn't explicitly specified.

In addition:

• If PublishSelfContained wasn't explicitly set to false, the publish properties PublishSingleFile and PublishAot implied a RuntimeIdentifier and therefore SelfContained (if it wasn't specified) during operations including dotnet build, dotnet restore, and dotnet publish.
• The PublishTrimmed property did not imply SelfContained.
• The PublishReadyToRun property implied SelfContained if SelfContained wasn't specified.

Starting in .NET 8, for apps that target .NET 8 or a later version, RuntimeIdentifier no longer implies SelfContained by default. Instead, apps that specify a runtime identifier are dependent on the .NET runtime by default (framework-dependent). Apps that target .NET 7 or earlier versions aren't affected.

In addition:

• If PublishSelfContained isn't explicitly set to false, the publish properties PublishSingleFile and PublishAot now imply SelfContained (if it's not specified) during dotnet publish only (that is, not for dotnet build or dotnet restore).
• The PublishTrimmed property also now implies SelfContained during dotnet publish.
• The PublishReadyToRun property no longer implies SelfContained if the project targets .NET 8 or later.

.NET 8 Preview 5

This change can affect source compatibility and binary compatibility.

• The new .NET SDK behavior aligns with Visual Studio behavior.
• Framework-dependent apps are smaller by default, since there aren't copies of .NET stored in each app.
• When .NET is managed outside of the app (that is, for framework-dependent deployments), .NET stays more secure and up-to-date. Apps that have their own copy of the runtime don't get security updates. This change makes more apps framework-dependent by default.
• Ideally, command-line options are orthogonal. In this case, the tooling supports both RID-specific self-contained deployment (SCD) and RID-specific framework-dependent deployment (FDD). So it didn't make sense that no RID defaulted to FDD and RID defaulted to SCD. This behavior was often confusing for users.

.NET 6 alerted users to this breaking change with the following warning:

warning NETSDK1179: One of '--self-contained' or '--no-self-contained' options are required when '--runtime' is used.

Now that customers have had time to add SelfContained explicitly, it's okay to introduce the break.

• If you're using .NET 7 or an earlier version and relied on the previous behavior where SelfContained was inferred, you'll see this warning:

  For projects with TargetFrameworks >= 8.0, RuntimeIdentifier no longer automatically gives a SelfContained app. To continue creating a .NET framework independent app after upgrading to 8.0, consider setting SelfContained explicitly.

  Follow the guidance of the warning and declare your app as self-contained. You can do that either in the project file or as a command-line argument, for example, dotnet publish --self-contained.

• If you're using .NET 8 and want to keep the previous behavior, set SelfContained to true in the same way as previously described.

SelfContained is an MSBuild property that you can insert into your project file, which is a file that has a .csproj, .vbproj, or .fsproj extension. Set the property as follows:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    ...
    <SelfContained>true</SelfContained>
  </PropertyGroup>
</Project>

• .NET application publishing overview