Microsoft has announced .NET 11, the latest version of its free, open-source, cross-platform development platform, introducing C# 15, hundreds of runtime optimizations, faster SDK tooling, and improvements across ASP.NET Core, Blazor, and .NET MAUI.
One headline change is C# 15, which introduces union types, allowing developers to define values representing one of several specified types. The compiler can then check whether switch expressions handle every case, helping catch missing conditions at compile time.
C# 15 also introduces closed class hierarchies, which restrict direct inheritance to the declaring assembly. Other language additions include extension indexers, collection expression arguments, and labeled break and continue statements.
In terms of performance, .NET 11 includes hundreds of optimizations targeting execution speed, memory usage, and code quality. The JIT compiler can now eliminate more redundant bounds checks and branches, perform additional devirtualization, and optimize operations when inputs are known at compile time.
Native AOT also sees improvements, particularly in interface dispatch, where a shared helper reduces generated code size and improves performance for workloads that make frequent interface calls. Hardware acceleration has been expanded with FP16 instruction support on compatible x64 and Arm64 processors.
Developers should notice improvements in everyday command-line operations. The .NET 11 SDK enables a Native AOT-based CLI host by default, allowing lightweight commands to run without starting the managed CLI. A persistent MSBuild server further reduces startup overhead between commands.
For Linux and macOS users, SDK installers are smaller thanks to assembly deduplication. Linux also gains in-process crash reporting that captures managed stack traces, loaded module information, and runtime state before an application exits.
Another change concerns asynchronous programming. .NET 11 introduces a new Runtime Async execution model that handles asynchronous suspension and resumption directly in the runtime instead of relying on compiler-generated state machines. However, Runtime Async remains an opt-in preview feature.
The standard libraries have received several additions, including built-in Zstandard compression through System.IO.Compression, expanded process execution APIs, and new in-memory stream adapters that let existing memory buffers be used as streams without copying their contents.
System.Text.Json now supports C# union types, F# discriminated unions, and JSON Lines output from asynchronous sequences. LINQ gains a FullJoin operator that preserves unmatched elements from both input collections.
For web development, ASP.NET Core 11 introduces asynchronous validation, letting validation rules perform database lookups or other I/O operations without blocking threads. OpenAPI 3.2 is now the default for generated API documentation, while SignalR connections can refresh authentication credentials without reconnection.
Blazor receives a new CacheView component for caching rendered component output during static server-side rendering. Interactive Server applications can optionally pause inactive browser sessions to release server resources.
Microsoft has expanded AI development support as well. The SDK now includes an MCP server project template, while experimental Blazor AI components provide support for streaming conversations, tool execution, and user approval workflows.
On top of that, .NET MAUI 11 adopts CoreCLR as its default runtime across supported platforms and improves XAML Hot Reload, native controls, and mobile application testing.
Entity Framework Core 11 also improves SQL generation by eliminating unnecessary joins in more scenarios, expanding GroupBy translation, and supporting LINQ FullJoin translation on compatible relational database providers.
Finally, developers should note that .NET 8 and .NET 9 reached end of support on November 10, 2026. Microsoft recommends moving to a supported version to continue receiving security and maintenance updates.
For additional details, see Microsoft’s announcement. .NET 11 is available for download from the official .NET website, with SDKs and runtimes for Linux, Windows, and macOS.
Keep in mind that .NET 11 is a Standard Term Support release with two years of support. Developers preferring a longer lifecycle can continue using .NET 10, which remains an LTS release.
