7 Key Highlights from .NET 11 Preview 4 You Can't Miss

Introduction

.NET 11 Preview 4 has officially landed, bringing a wave of enhancements that touch nearly every corner of the development ecosystem. From long-awaited library updates and JIT optimizations to smarter SDK tools and expanded mobile support, this release is packed with features designed to boost productivity and performance. Whether you're building ASP.NET Core backends, cross-platform desktop apps with .NET MAUI, or working with Entity Framework Core, there's something here for you. Dive into the seven most important updates you need to know about—and get ready to download the preview today.

1. Libraries: The Process Gets Its Biggest Update in Years

The Process class, a staple for system-level operations, receives a major overhaul in .NET 11 Preview 4. Developers can expect improved performance and new capabilities that simplify working with system processes. Beyond that, the release introduces Span-based APIs for Deflate, ZLib, and GZip compression and decompression, enabling more efficient memory management and faster data handling. Floating-point hex formatting and parsing are now available, making it easier to work with IEEE 754 representations. The System.Text.Json library also gets multiple enhancements, including better serialization options and performance tweaks. For a complete list of all library improvements, check the official release notes.

2. Runtime: JIT Optimizations and Hardware Intrinsics Take Center Stage

The .NET runtime receives a notable performance boost in Preview 4. Runtime libraries are now compiled with runtime-async, improving asynchronous execution efficiency. The JIT compiler introduces several optimizations that reduce code size and execution time, while hardware intrinsics and code generation enhancements allow developers to harness CPU-specific instructions more effectively. These changes mean faster application startup and smoother runtime behavior, especially for compute-intensive workloads. Whether you're running microservices or desktop apps, the runtime improvements will be felt across the board. See all updates in the runtime section.

3. SDK: Smarter Tooling with Device Selection and Telemetry Changes

The .NET SDK in Preview 4 brings several quality-of-life improvements. The dotnet watch command now supports device selection for .NET MAUI and mobile projects, making it easier to target specific emulators or physical devices during development. Fish shell completions join the existing Bash, Zsh, and PowerShell support, giving Fish users full command-line productivity. Commands like dotnet reference now fall back to the current directory, reducing friction. Notably, OpenTelemetry replaces Application Insights for CLI telemetry, aligning with modern observability standards. Explore all SDK updates here.

4. C#: Clearer Diagnostics and Compilation Cache

C# developers will appreciate two key refinements in Preview 4. First, clearer diagnostics for misplaced #! shebang directives help catch syntax errors early, especially in scripts. Second, the VBCSCompiler build server now supports an opt-in compilation cache, which can significantly speed up repeated builds by reusing previously compiled units. This is a boon for large projects where compilation time is a bottleneck. While not a full language feature release, these improvements make day-to-day coding smoother. For more details, refer to the C# updates.

5. ASP.NET Core: OpenAPI Enhancements and Blazor Upgrades

ASP.NET Core Preview 4 introduces several modern web development features. The HTTP QUERY method is now included in generated OpenAPI documents, aligning with the latest HTTP standards. Blazor receives two notable additions: SupplyParameterFromTempData allows seamless data passing across pages, and server-initiated Blazor Server circuit pauses give developers more control over connection management. Most excitingly, an MCP Server template ships directly with the .NET SDK, making it easier to build Model Context Protocol servers. Check out all ASP.NET Core updates here.

6. .NET MAUI: Targeted Device Support via dotnet watch

Mobile developers using .NET MAUI gain significant debugging and deployment capabilities in Preview 4. The dotnet watch tool now supports hot reload for Android and iOS, enabling rapid iteration without rebuilding. Combined with the new device selection feature (mentioned in SDK), you can now preview your app on specific emulators or physical devices instantly. This dramatically improves the development experience for cross-platform apps. Whether you're fine-tuning UI or testing platform-specific APIs, these enhancements reduce turnaround time. For a full rundown, see the .NET MAUI updates.

7. Entity Framework Core: Vector Search and JSON Enhancements

Entity Framework Core in Preview 4 brings powerful new features for data-intensive applications. Approximate vector search for SQL Server 2025 enables fast similarity queries, ideal for AI and machine learning workloads. JSON mapping is now fully integrated into the relational model, allowing you to work with JSON columns seamlessly. Additionally, temporal period properties can map to CLR properties, simplifying time-based data handling. The dotnet ef tool also gains the ability to read defaults from a dotnet-ef.json file, streamlining configuration. Discover all EF Core updates here.

Conclusion

.NET 11 Preview 4 is a substantial step forward, with improvements that span the entire stack. From enhanced library APIs and runtime efficiency to smarter SDK tooling and mobile development support, every developer will find something to love. To get started, download the .NET 11 SDK. Windows users can pair it with Visual Studio 2026 Insiders; others can use Visual Studio Code with the C# Dev Kit extension. Dive into the preview and start exploring the future of .NET today!