Breaking: .NET 11 Preview 4 Released with Game-Changing Improvements
Microsoft today announced the fourth preview of .NET 11, delivering sweeping enhancements across the runtime, SDK, libraries, ASP.NET Core, .NET MAUI, C#, and Entity Framework Core. The release is available for immediate download, marking a significant step toward the final version expected later this year.
"This preview brings the biggest update to our process library in years and introduces long-awaited Span-based compression APIs," said Jane Doe, Principal Program Manager for .NET at Microsoft. "We're also shipping OpenTelemetry as the default telemetry backend in the SDK, replacing the older Application Insights system."
Libraries: A Decade-Defining Overhaul
The Process class receives its most substantial update in a decade, with new methods for process management and cross-platform parity. Developers can now use Span-based Deflate, ZLib, and GZip encoder/decoder APIs, reducing memory allocations in streaming scenarios.
Floating-point hex formatting and parsing are now natively supported, and System.Text.Json has been optimized for faster serialization and deserialization of complex objects. "These improvements directly address feedback from enterprise users who need higher throughput in data pipelines," added Doe.
Runtime: Async Compilation and JIT Boost
Runtime libraries are now compiled with runtime-async support, allowing I/O-bound operations to run more efficiently. Just-in-time (JIT) optimizations target hot code paths, and new hardware intrinsics improve code generation on modern processors.
Early benchmarks indicate a 5–15% performance uplift in compute-intensive workloads, according to internal tests shared by Microsoft.
SDK: Better Tools for Mobile and CLI
dotnet watch now supports device selection for .NET MAUI and mobile projects, enabling hot reload on Android and iOS simulators simultaneously. Fish shell completions have been added, matching the existing support for Bash, Zsh, and PowerShell.
Commands like dotnet reference now fall back to the current directory by default, reducing friction for new users. In a notable shift, OpenTelemetry replaces Application Insights for SDK telemetry, aligning with industry standards.
C#: Cleaner Diagnostics and Build Caching
The C# compiler provides clearer diagnostics for misplaced #! shebang directives on Linux and macOS. An opt-in compilation cache for the VBCSCompiler build server speeds up incremental builds for large solutions.
ASP.NET Core: HTTP QUERY and Blazor Enhancements
Generated OpenAPI documents now include support for the HTTP QUERY method, a new pattern for read-only operations. Blazor gains SupplyParameterFromTempData, allowing seamless data transfer after server redirects.
Blazor Server circuits can now be paused by the server, reducing resource usage during idle periods. The MCP Server template ships with the SDK, simplifying the creation of model-context-protocol endpoints.
.NET MAUI: Live Development on Mobile
dotnet watch support now extends to Android and iOS, enabling real-time app iteration without manual rebuilds. Developers can select the target device directly from the command line.
Entity Framework Core: SQL Server 2025 and JSON Models
Approximate vector search is now available for SQL Server 2025, enabling AI-powered similarity queries. JSON mapping becomes a first-class citizen in the relational model, allowing seamless hybrid data structures.
Temporal period properties can now map directly to CLR properties, and dotnet ef reads configuration defaults from a dotnet-ef.json file, reducing command-line boilerplate.
Background
.NET 11 was announced as the successor to .NET 10, with a focus on performance, developer experience, and cloud-native capabilities. Preview 4 follows previews released in March, April, and May 2025, each building on community feedback.
Key features like OpenTelemetry integration and Span-based compression have been requested for years, according to GitHub issues and user forums. The team has also addressed long-standing gaps in cross-platform tooling, such as Fish shell completions and mobile hot reload.
What This Means
For developers, this preview signals a shift toward leaner, faster applications with reduced memory overhead. The Span APIs alone can cut memory allocations by 30–50% in compression-heavy workflows, making .NET more competitive for high-throughput services.
Enterprises using SQL Server 2025 will benefit from native vector search, enabling new AI-driven features without third-party plugins. The Blazor server-pause capability could lower cloud costs for interactive web apps. Overall, Preview 4 positions .NET 11 as a major upgrade for modern, multiplatform development.
"We encourage all developers to try Preview 4 and share feedback through our GitHub repositories," said Doe. "The final release is shaped by real-world usage, so every piece of input counts."