Breaking changes in .NET 8

If you're migrating an app to .NET 8, the breaking changes listed here might affect you. Changes are grouped by technology area, such as ASP.NET Core or Windows Forms.

This article categorizes each breaking change as binary incompatible or source incompatible, or as a behavioral change:

  • Binary incompatible - When run against the new runtime or component, existing binaries may encounter a breaking change in behavior, such as failure to load or execute, and if so, require recompilation.

  • Source incompatible - When recompiled using the new SDK or component or to target the new runtime, existing source code may require source changes to compile successfully.

  • Behavioral change - Existing code and binaries may behave differently at run time. If the new behavior is undesirable, existing code would need to be updated and recompiled.


This article is a work in progress. It's not a complete list of breaking changes in .NET 8. To query breaking changes that are still pending publication, see Issues of .NET.

Core .NET libraries

Title Type of change Introduced
Activity operation name when null Behavioral change Preview 1
AnonymousPipeServerStream.Dispose behavior Behavioral change Preview 1
Backslash mapping in Unix file paths Behavioral change Preview 1
FileStream writes when pipe is closed Behavioral change Preview 1
GetFolderPath behavior on Unix Behavioral change Preview 1
ITypeDescriptorContext nullable annotations Source incompatible Preview 1
Legacy Console.ReadKey removed Behavioral change Preview 1


Title Type of change Introduced
AesGcm authentication tag size on macOS Behavioral change Preview 1
RSA.EncryptValue and RSA.DecryptValue obsolete Source incompatible Preview 1


Title Type of change Introduced
ActivatorUtilities.CreateInstance behaves consistently Behavioral change Preview 1
ActivatorUtilities.CreateInstance requires non-null provider Behavioral change Preview 1
ConfigurationBinder throws for mismatched value Behavioral change Preview 1
HostApplicationBuilderSettings.Args respected by HostApplicationBuilder ctor Behavioral change Preview 2


Title Type of change Introduced
TwoDigitYearMax default is 2049 Behavioral change Preview 1


Title Type of change Introduced
IntPtr no longer used for function pointer types Behavioral change Preview 2


Title Type of change Introduced
CLI console output uses UTF-8 Behavioral change/Source and binary incompatible Preview 1
'dotnet pack' uses Release configuration Behavioral change/Source incompatible Preview 1
'dotnet publish' uses Release configuration Behavioral change/Source incompatible Preview 1

Windows Forms

Title Type of change Introduced
Anchor layout changes Behavioral change Preview 1
DefaultValueAttribute removed from some properties Behavioral change Preview 2
ExceptionCollection ctor throws ArgumentException Behavioral change Preview 1
Forms scale according to AutoScaleMode Behavioral change Preview 1
ImageList.ColorDepth default is Depth32Bit Behavioral change Preview 1
TableLayoutStyleCollection throws ArgumentException Behavioral change Preview 1
Top-level forms scale minimum and maximum size to DPI Behavioral change Preview 1
WFDEV002 obsoletion is now an error Source incompatible Preview 1

See also