Microsoft has released .NET 11, the latest version of its free, open-source developer platform, launching it on the opening day of the .NET Conf 2026 virtual conference on 10 November. The release brings a new version of the C# programming language, faster command-line tooling and a set of libraries aimed squarely at developers building AI-powered applications.

The .NET team announced the release on its official blog, describing a version focused on speed and productivity, with hundreds of runtime optimisations, more responsive software development kit (SDK) tooling and less waiting on everyday commands. The conference runs until 13 November, with product team sessions on 10 and 11 November followed by two days of community sessions.

C# 15 headlines the release

C# 15 is now the default language version for projects targeting .NET 11. Its most notable addition is union types, which let a value be one of a declared set of case types, with the compiler checking that switch expressions handle every possibility. A product lookup, for example, can now be typed as either a found product or a not-found result, rather than relying on a generic base class or an untyped object.

The language also adds closed hierarchies, which limit direct derivation to the declaring assembly so the compiler can check patterns across the whole hierarchy, along with smaller everyday improvements such as extension indexers and labelled break and continue statements. F# 11 arrives alongside it, with lower compiler memory use and fewer allocations in collection operations.

Faster tooling and a shorter wait

Day-to-day development should feel quicker. The SDK now enables a Native AOT command-line host by default, so simple commands such as help and version queries can run without starting the managed command-line interface, and the MSBuild server stays warm between invocations instead of starting from cold each time. Installers on Linux and macOS are smaller through assembly deduplication, and file-based apps can now span several source files using the #:include directive.

On the runtime side, Microsoft points to work across the just-in-time compiler, which removes more redundant bounds checks and branches, and to Native AOT interface dispatch that reduces the code needed at interface call sites. Hardware support has also expanded, including FP16 instructions for Half operations on supported x64 and Arm64 hardware. One feature remains in preview: Runtime Async, which moves asynchronous suspension and resumption into the runtime itself and gives profilers and debuggers a clearer live call stack.

AI development moves into the platform

The release leans heavily into agentic development. The .NET 11 SDK includes a template for building a Model Context Protocol (MCP) server, giving AI applications a common way to discover and call tools, while Microsoft.Extensions.AI provides abstractions for model access, caching and observability. The Microsoft Agent Framework builds on those abstractions with agents that call tools and maintain conversation state, plus workflows that coordinate agents and application code.

Microsoft has also added .NET Skills, task-specific guidance for coding agents, a .NET Upgrade canvas for reviewing modernisation progress, and an experimental .NET MAUI DevFlow toolkit that exposes a running app's visual tree and screenshots so an agent can inspect and test it. Experimental Blazor AI components integrate with the Agent User Interaction Protocol for agentic web experiences.

Web, mobile and data updates

ASP.NET Core brings asynchronous validation, OpenAPI 3.2 support and new capabilities for Blazor and SignalR applications. .NET MAUI adopts CoreCLR as its default runtime and improves XAML iteration and native controls. The libraries add built-in Zstandard compression, simpler process execution, richer JSON support and a new LINQ FullJoin operator, which preserves unmatched elements from both sides of a join.

Entity Framework Core 11, which requires .NET 11, removes unnecessary joins in more scenarios, improves GroupBy translation and adds experimental support for SQL Server vector indexes and approximate vector search, aimed at applications that combine relational data with AI workloads.

Support: two years, and a deadline for older versions

.NET 11 is a Standard Term Support release, supported for two years. .NET 10 remains the long-term support option for teams that prefer a longer window. The timing matters for anyone still on older versions: .NET 8 and .NET 9 reached end of support on 10 November, the same day .NET 11 shipped, so those teams will need to move to .NET 10 or .NET 11 to keep receiving security patches.

Microsoft has published the full list of what is new in .NET 11 on Microsoft Learn, and the SDK and runtimes are available to download from the .NET website. Developers can follow the remaining .NET Conf sessions, including the Day 1 keynote, through the conference site.

Sources: Microsoft .NET Blog: Announcing .NET 11 and Thurrott: Microsoft Releases .NET 11.