Microsoft has shipped two preview releases of .NET 11, and there’s a fair amount to dig into. Here’s a rundown of the most notable changes.
<h2>Runtime async gets a real overhaul</h2>
Runtime Async V2 moves the async/await state machine logic out of the compiler and into the runtime itself. The practical upside: less overhead, better diagnostics, and no code changes required. This one has been a long time coming and should improve performance for async-heavy workloads without developers having to do anything.
<h2>Native Zstandard compression</h2>
Zstandard (zstd) is now built into the BCL. It decompresses 2–7x faster than GZip or Brotli, which matters a lot for scenarios like serving large payloads or reading compressed data at scale. No third-party packages needed.
<h2>Blazor changes</h2>
There are several Blazor additions worth knowing about.
TempData for static SSR components works the same way it does in MVC and Razor Pages - stored in cookies, no extra registration required. This makes Post-Redirect-Get patterns and flash messages straightforward to implement in static SSR Blazor.
IHostedService support in Blazor WebAssembly lets you run background tasks in the browser. Useful for polling, timers, or anything that needs to run independently of the UI.
A new web worker template (<code>dotnet new webworker</code>) makes it easier to offload CPU-heavy work off the main thread.
Relative URI navigation via <code>RelativeToCurrentUri</code> handles navigation relative to the current page rather than the app root.
Built-in Label and DisplayName form components reduce boilerplate when building forms.
An Environment component lets you conditionally render content based on the current environment (development, production, etc.).
A BasePath component replaces hardcoded <code>&lt;base href&gt;</code> tags, which is a small but welcome cleanup.
Easier SignalR configuration for Blazor Server via <code>AddInteractiveServerRenderMode</code> simplifies setup.
<h2>EF Core vector search</h2>
EF Core now supports native SQL Server vector search through LINQ, backed by DiskANN indexes. You can run semantic similarity queries without leaving the ORM. This is the kind of feature that would have required raw SQL or a separate library before.
<h2>Other highlights</h2>
<ul>
<li>BFloat16 support for ML workloads</li>
<li>C# collection expression arguments - a small ergonomic improvement</li>
<li>Native OpenTelemetry tracing built into <a href="http://ASP.NET" target="_blank" rel="noopener nofollow">ASP.NET</a> Core</li>
<li>Smaller SDK container images - up to 17% reduction in size</li>
<li>MAUI/Android improvements with CoreCLR now the default runtime</li>
<li>CLI improvements to <code>dotnet run</code>, <code>dotnet test</code>, and <code>dotnet watch</code></li>
</ul>
Overall these previews feel like a mix of long-requested quality-of-life fixes (Blazor TempData, BasePath) and more substantial infrastructure work (Runtime Async V2, native zstd). The EF Core vector search addition is probably the most interesting for teams building anything AI-adjacent on SQL Server.

Collections

.NET 11 Previews 1 and 2 introduce Runtime Async V2, which moves async/await state machine logic into the runtime for lower overhead and better diagnostics. Native Zstandard compression is now built into the BCL, offering 2–7x faster decompression than GZip or Brotli. Blazor gains TempData for static SSR, IHostedService support in WebAssembly, a new web worker template, relative URI navigation, built-in form label components, an Environment component, a BasePath component, and simplified SignalR configuration. EF Core adds native SQL Server vector search via LINQ with DiskANN indexes. Additional highlights include BFloat16 support for ML, native OpenTelemetry tracing in ASP.NET Core, up to 17% smaller SDK container images, MAUI/Android improvements with CoreCLR as the default runtime, and CLI enhancements.

.NET 11 Preview 1 and 2: what's new across runtime, Blazor, EF Core, and more