The short version
If your production apps still run on .NET 8 or .NET 9, they stopped getting security fixes on November 10, 2026. Your supported targets are now .NET 10 LTS or the new .NET 11. Both lose support on the same day in November 2028, so .NET 11 no longer means a shorter runway. For teams that run .NET development in-house or with a vendor, the upgrade belongs in this quarter’s plan.
What did Microsoft release on November 10?
Microsoft shipped .NET 11 as the main launch of .NET Conf 2026. The release bundles C# 15, F# 11, runtime and library updates, and changes across ASP.NET Core, Blazor, .NET MAUI and the SDK.
The same day, both .NET 8 and .NET 9 reached end of support. Microsoft published their final patches, 8.0.34 and 9.0.23. New vulnerabilities in those runtimes won’t be fixed. That’s the whole problem.
Which .NET versions are still supported?
Two versions are supported today: .NET 10 and .NET 11. Microsoft’s support policy now gives STS releases two years instead of 18 months. As a result, the odd-numbered release and the LTS release before it end on the same date.
| Version | Type | Released | End of support | Status |
|---|---|---|---|---|
| .NET 8 | LTS | Nov 14, 2023 | Nov 10, 2026 | Out of support |
| .NET 9 | STS | Nov 12, 2024 | Nov 10, 2026 | Out of support |
| .NET 10 | LTS | Nov 11, 2025 | Nov 14, 2028 | Supported |
| .NET 11 | STS | Nov 10, 2026 | Nov 14, 2028 | Supported |
Source: Microsoft .NET support policy, checked November 12, 2026.
What’s new in .NET 11 and C# 15?
C# 15 language features
- Union types. A value can be one of a declared set of case types. The compiler checks that a
switchexpression handles every case. - Closed hierarchies. A base class can limit direct inheritance to its own assembly, so the set of subtypes is known.
- Smaller additions round it out: collection expression arguments, extension indexers, and labeled
breakandcontinue.
Web, mobile and tooling changes
- ASP.NET Core: OpenAPI 3.2 is the default, Minimal APIs and forms support asynchronous validation, and SignalR can refresh authentication without reconnecting.
- .NET MAUI: CoreCLR is now the default runtime on all platforms. On Apple platforms, where JIT isn’t allowed, it uses precompiled code and an interpreter. Native AOT for Android stays experimental.
- SDK: CLI commands start through a Native AOT host, and the MSBuild server stays warm between builds. The new
dotnetuptoolchain manager is in public preview. - AI: the SDK ships a
dotnet new mcpservertemplate next to Microsoft.Extensions.AI and Microsoft Agent Framework. - Runtime async, which moves async suspension into the runtime for clearer stack traces, is still a preview and opt-in only.
What can break when you upgrade?
Microsoft lists a few changes that need attention before a production move:
- Minimum CPU requirements have been raised. Check older build agents, VMs and on-premises servers against the compatibility notes.
- Entity Framework Core 11 requires .NET 11. Standardize on .NET 10 and you stay on EF Core 10.
- The optional
Microsoft.Maui.Controls.Compatibilitypackage no longer ships, so older Xamarin.Forms-style code must be migrated. - Development needs an up-to-date Visual Studio 2026 or VS Code with C# Dev Kit.
What it means for US & EU software teams
Why is an unsupported runtime a compliance risk?
An unsupported runtime is now a compliance finding, not just technical debt. SOC 2 auditors, PCI DSS assessors and buyers’ security questionnaires often ask whether production software gets vendor patches. In the EU, NIS2 and DORA push regulated companies and their suppliers in the same direction. A .NET 8 API that was fine in October is an open item today.
Should you move to .NET 10 or .NET 11?
Choosing between .NET 10 and .NET 11 is simpler than in past years. Because both end on November 14, 2028, .NET 11 no longer trades support length for features. The real question is how often you want to upgrade:
- Pick .NET 10 if you depend on third-party libraries or vendor SDKs that certify only LTS releases, or if your change-approval process is slow.
- Pick .NET 11 if you want C# 15 unions, EF Core 11, CoreCLR in MAUI or the faster CLI, and you can test against a new release each November.
Either way, if Microsoft keeps its annual November cadence, .NET 12 LTS arrives in November 2027 and the cycle repeats. So budget upgrades as recurring work. They aren’t a one-off project anymore.
What should teams do this quarter?
- Inventory runtimes. List every service, function, container image and desktop app by target framework, including
global.jsonpins and base images. - Rank by exposure. Move internet-facing APIs and apps that process payment or health data first.
- Pick a target. Choose .NET 10 or .NET 11 per product, using the rules above, and record the decision.
- Check dependencies. Confirm NuGet packages, ORMs and vendor SDKs support the target, and check CPU requirements on build agents.
- Upgrade in slices. Move shared libraries first, run the full test suite and a staged rollout, then retire the old images.
Frequently asked questions
When did .NET 8 and .NET 9 reach end of support?
Both reached end of support on November 10, 2026, the day .NET 11 was released. Their final patches are 8.0.34 and 9.0.23. After that date Microsoft no longer ships security fixes, bug fixes or technical support for them.
Is .NET 11 an LTS release?
No. .NET 11 is a Standard Term Support (STS) release with two years of support. Under Microsoft's current policy its support ends on November 14, 2028, the same day as .NET 10, which is the current Long Term Support release.
Should we upgrade to .NET 10 or .NET 11?
Both are supported until November 14, 2028, so the choice is about features and upgrade rhythm. Choose .NET 10 if your libraries or vendor SDKs certify only LTS releases. Choose .NET 11 if you want C# 15 union types, EF Core 11 or CoreCLR in .NET MAUI and can test a new release every year.
What are union types in C# 15?
A union type declares that a value can be one of a fixed set of case types. The compiler converts from those types and checks that switch expressions handle every case, which removes a class of missed-case bugs. Closed hierarchies, which limit inheritance to the declaring assembly, ship alongside them.
What should we check before moving production apps to .NET 11?
Check the raised minimum CPU requirements on servers and build agents, confirm that NuGet packages and vendor SDKs support .NET 11, plan for EF Core 11, and update to a current Visual Studio 2026. .NET MAUI apps that used the Microsoft.Maui.Controls.Compatibility package need migration because it no longer ships.
Sources
Microsoft .NET Blog — Announcing .NET 11 (primary source, November 10, 2026)
Microsoft — .NET and .NET Core official support policy (end-of-support dates)
Visual Studio Magazine — .NET 11 Ships with C# 15 Unions, Faster Tools and CoreCLR for MAUI (November 10, 2026)
ITdaily — Microsoft releases .NET 11 with C# 15 and CoreCLR for MAUI (November 2026)