Microsoft announced the availability of .NET 11 Release Candidate 1 on September 8, 2026, as a broad prerelease ahead of the final release. The update includes changes and improvements in libraries, the runtime, SDK, MSBuild, and NuGet, in addition to C#, F#, ASP.NET Core, .NET MAUI, and Windows Forms.
Platform and Development Tool Improvements
.NET 11 libraries add capabilities for handling system processes and checking their completion status, resolving DNS records on Linux, and supporting JSON for new numeric types and binary schemas. The release also includes support for closed polymorphism and unions in JSON, asynchronous options validation, creating BitArray values from extended memory, and reusing compression and decompression encoders.
The security layer includes experimental caller-driven TLS sessions, TLS channel binding on Unix, and AES Key Wrap support, along with improved authenticated-encryption speed on Apple platforms. The release also records breaking changes and bug fixes, while acknowledging community contributions.
What Changes Practically for Developers?
At the runtime level, .NET 11 adds in-process crash reporting on Unix, while FP16 operations use specialized hardware instructions. In the SDK, mobile application testing improves through dotnet test, with the addition of run-level control and new result formats. Container publishing produces reproducible images and avoids repeated uploads, while file-based programs gain support for reusing Native AOT and formatting.
Other improvements include limiting dotnet format configuration discovery to included files, adding tar archive creation and extraction in MSBuild, and enabling build tools to access glob item patterns. NuGet reuses project evaluations during packing, and vulnerable package updates now work with settings that treat warnings as errors.
Languages and Application Frameworks
C# 15 stabilizes unions and other language features, with improvements to the evolution of unsafe usages. F# adds record spreading, record constructors, and direct delegate creation, along with more efficient interpolated strings and formatting for records and unions without relying on reflection.
In ASP.NET Core, SignalR authentication-update APIs are now final, with update support in the TypeScript client. Blazor Server circuits also update after authentication changes, and OpenAPI reflects deprecated APIs, with the ability to select an environment for generating OpenAPI during the build and to use TLS channel binding in Negotiate authentication.
The release also covers testing, controls, platform features, and XAML in .NET MAUI; updates to .NET for Android and Apple platforms; as well as kiosk-mode experiment management and the stability of modern visual styles in Windows Forms for RC 1.
Availability and What to Consider
Developers can get started by installing the .NET 11 SDK. Microsoft recommends using the latest version of Visual Studio 2026 Insiders on Windows, with Visual Studio Code and the C# Dev Kit extension also available. The scope of the changes indicates that the release is important for teams working on web services, containers, and mobile applications, but because it is a Release Candidate, production teams need to review the complete release notes and compatibility changes before adopting it definitively. Microsoft also provides separate pages covering what is new in .NET 11, C# 15, ASP.NET Core, and Entity Framework Core, along with breaking changes and .NET releases.