.NET 11 Preview 1 Just Dropped. Here’s What Enterprise Teams Should Actually Be Paying Attention To.

Microsoft just released .NET 11 Preview 1, and the developer community is doing what it does best: getting excited about new toys. Runtime async improvements. CoreCLR on WebAssembly. Zstandard compression. BFloat16 floating-point support. Collection expression arguments in C#. It’s a solid preview drop.

But while everyone is reading the release notes and spinning up preview SDKs, there’s a much bigger story that most .NET teams aren’t talking about—and it’s happening nine months from now.

On November 10, 2026, both .NET 8 and .NET 9 hit end of support. On the same day. At the same time. No extensions.

If your enterprise is running production workloads on either version, this isn’t a “we’ll get to it eventually” situation. This is a hard deadline with real consequences for security, compliance, and operational stability.
‍

What’s Actually in .NET 11 Preview 1

Credit where it’s due—.NET 11 Preview 1 is a meaningful release. Microsoft is clearly investing in performance, developer experience, and broadening platform reach. Here are the highlights worth knowing:

Runtime Async is the headline feature. This introduces new runtime-level infrastructure for async methods, with the goal of improving both tooling and performance for async-heavy codepaths. CoreCLR support for RuntimeAsync is now enabled by default—no environment variables needed. For teams running high-throughput services, this is a genuine performance unlock.

CoreCLR on WebAssembly signals Microsoft’s growing investment in running .NET natively in the browser. Combined with XAML Source Generation becoming default in .NET MAUI and CoreCLR becoming the default runtime for Android, Microsoft is clearly pushing toward a unified runtime story across every platform.

On the libraries side, Zstandard compression support, the new BFloat16 type (critical for AI/ML workloads), and HMAC/KMAC verification APIs all point toward .NET positioning itself as a platform that can compete in modern, performance-sensitive domains.

Entity Framework Core gets complex types with TPT/TPC inheritance (and JSON column support) and one-step migration creation—quality-of-life improvements that EF Core-heavy teams will appreciate. ASP.NET Core and Blazor pick up several component improvements and better OpenAPI support.

It’s a strong preview.

‍

The Real Story: The November 2026 EOL Convergence

Here’s the situation most enterprise .NET teams are sitting in right now:

.NET 8 (LTS) launched in November 2023 with three years of support. .NET 9 (STS) launched in November 2024 with what was originally 18 months of support. Then, in late 2025, Microsoft extended STS support from 18 to 24 months. The result? Both .NET 8 and .NET 9 now reach end of support on exactly the same date: November 10, 2026.

That’s unusual. Typically, organizations on an LTS release have a comfortable runway while the next version matures. But this time, the safety net disappears for both versions simultaneously. Teams that chose .NET 8 for stability and teams that adopted .NET 9 for the latest features are all facing the same cliff.

‍

‍

*Estimated based on Microsoft’s annual release cadence. .NET 11 Preview 1 released February 10, 2026.

After November 10, 2026, applications running on .NET 8 or .NET 9 will no longer receive security patches, bug fixes, or compliance updates from Microsoft. Full stop.

‍

Why This Matters More Than You Think

Nine months sounds like plenty of time. It isn’t. Here’s why:

Migration timelines are always longer than estimated. Moving from .NET 8 to .NET 10 isn’t just a framework swap. It means auditing dependencies, updating third-party packages, testing for breaking changes, retraining teams, and running parallel environments during the transition. For enterprise applications with complex dependency trees, this routinely takes 6–12 months.

Third-party ecosystem readiness is uneven. While major libraries like Serilog and NLog confirmed .NET 10 compatibility quickly, enterprise tooling from vendors like ComponentOne and Telerik historically takes months to certify new versions. If your application depends on one of those slower-moving vendors, your migration timeline is dictated by theirs.

Compliance doesn’t wait for migration plans. If your organization is subject to PCI-DSS, HIPAA, SOC 2, FedRAMP, or similar frameworks, running unsupported software is a compliance violation. Auditors don’t care about your migration roadmap—they care about whether your production systems are receiving security patches.

Zero-day vulnerabilities don’t wait either. Once .NET 8 and .NET 9 go EOL, any newly discovered CVEs in those runtimes will not be patched by Microsoft. Your applications become progressively more exposed with every passing month.

Hidden vulnerabilities await. CVEs that may be reported for .NET 10+ that affect .NET 8 and 9 won’t be reported for .NET 8 or 9. Your security scanners may report .NET 8 or 9 applications and deployments as secure when they are vulnerable to active exploits.

‍

What Smart Teams Are Doing Right Now

The teams that handle this well aren’t the ones who panic in October. They’re the ones who started planning in Q1. Here’s what a proactive approach looks like:

1. Audit your .NET portfolio now.

Run dotnet list package --vulnerable and dotnet list package --outdated across every project. Know exactly what you’re running, what’s exposed, and what dependencies are blocking your path forward. You can’t plan a migration you can’t see.

2. Evaluate whether .NET 10 is your migration target.

.NET 10 (LTS) shipped in November 2025 with support through November 2028. It’s the natural landing zone for most teams. But “natural” doesn’t mean “simple.” Test in isolated branches, leverage the new GitHub Copilot app modernization feature , and deploy incrementally to non-production environments first.

3. Build a realistic timeline—then add buffer.

If your team estimates six months for migration, plan for nine. If a critical vendor hasn’t certified .NET 10 support yet, that’s not an assumption you can carry into production. Build contingency into the plan from day one.

4. Have a Plan B for applications that can’t migrate in time.

This is the part nobody wants to talk about, but it’s the most important. Some applications won’t make the November deadline. Maybe they have deep dependency issues. Maybe the team is stretched thin. Maybe the application is mission-critical and the risk of a rushed migration outweighs the risk of staying put.

For those applications, the question isn’t “how do we migrate faster?” It’s “how do we stay secure and compliant while we migrate at a pace that doesn’t break things?”

‍

Staying Secure When the Clock Runs Out

This is exactly the problem HeroDevs’ Never-Ending Support (NES) was built to solve. When Microsoft stops patching .NET 8 and .NET 9 in November 2026, NES picks up where they leave off—delivering ongoing security patches, CVE remediation, and compliance coverage for teams that need more time.

NES doesn’t replace your migration plan. It gives you breathing room to execute it without cutting corners. Your applications stay patched. Your compliance posture stays intact. And your team gets to migrate on a timeline that makes sense for the business—not one dictated by a support calendar.

We’ve been doing this for .NET 6 since it hit EOL in November 2024, and for teams running AngularJS, Spring, Rails, Drupal, and dozens of other frameworks that have aged out of official support. The playbook is the same: keep your production systems secure while you plan the next move.

‍

The Bottom Line

.NET 11 Preview 1 is exciting. It’s a glimpse at where the platform is heading, and the runtime async improvements and WASM investments are genuinely compelling. If you’re a forward-looking developer, you should absolutely be experimenting with it.

But if you’re an engineering leader responsible for production applications, the thing that should be occupying your attention right now isn’t November 2026’s new release—it’s November 2026’s EOL deadline.

Both .NET 8 and .NET 9 go end-of-life on November 10, 2026. That’s nine months from today. Start planning now.