Microsoft support for .NET 8 and .NET 9 ends on 10 November 2026. From that date the two versions get no more security fixes, servicing updates or technical support. Support for the in-process model in Azure Functions ends on the same day. Applications keep running, but new vulnerabilities in them will not be patched.
What happened
Microsoft's .NET team published an end-of-support notice on 29 June 2026, and its support policy page lists 10 November 2026 for both versions. InfoWorld reported the deadline on 1 July 2026.
| Product | Type | End of support | Supported replacement |
|---|---|---|---|
| .NET 8 | Long Term Support (LTS), released November 2023 | 10 November 2026 | .NET 10 (LTS), supported to 14 November 2028 |
| .NET 9 | Standard Term Support (STS), released November 2024 | 10 November 2026 | .NET 10 (LTS) |
| Azure Functions in-process model | Hosting model for C# function apps | 10 November 2026 | Isolated worker model |
| PowerShell 7.4 (LTS) | Listed on Microsoft's 2026 lifecycle page | 10 November 2026 | A supported PowerShell release |
Why two versions end on the same day. .NET 9 was first due to leave support in May 2026. In September 2025 Microsoft extended Standard Term Support releases from 18 to 24 months, starting with .NET 9, which moved its date to 10 November. Moving from .NET 8 to .NET 9 therefore gains nothing; the supported target is .NET 10.
What stops and what does not. Microsoft says applications built on .NET 8 or .NET 9 will continue to run. What ends is patching: security issues found after the date will not be fixed for those versions. Because 10 November is a Patch Tuesday, the .NET team said each version may receive one final update that day if a known critical issue needs it. Visual Studio 2022 will mark the .NET 8 and .NET 9 components as out of support in a later servicing update.
Azure Functions. Microsoft Learn's migration guide asks owners of C# function apps on the in-process model to move to the isolated worker model, targeting .NET 10 (or .NET Framework 4.8 where an app depends on Framework-only libraries). It recommends using a staging slot, because the runtime setting change and the code publish each restart the app, with a temporary mismatch error between them.
Other Microsoft products on the same date. Microsoft's lifecycle list also shows 10 November 2026 for Windows 11 Enterprise and Education version 23H2, Windows 11 IoT Enterprise version 23H2 and Azure IoT Edge 1.5.
What it means for businesses
These points are our reading of the change, not statements by Microsoft.
This is a security deadline, not an outage. Nothing switches off today. The risk grows over time: each new .NET vulnerability published after this date stays open on systems that were not upgraded.
Customer portals, internal tools, integrations and APIs are the likely exposure. Business systems built or upgraded since late 2023 are likely to target .NET 8, since it was the current LTS release. Systems that face the internet or handle payments and personal data carry the most risk.
Audits and contracts may notice before attackers do. Security questionnaires, cyber insurance forms and enterprise customer reviews can ask whether software runs on supported platforms.
Most upgrades are planned work, not a rewrite. Microsoft describes the basic step as changing the target framework to net10.0 and then updating development and hosting environments. The real effort sits in breaking changes, third-party packages and testing. Azure Functions apps need more work, because bindings, logging and start-up code change in the isolated model.
What to do next
- List what you run. For each application, note the .NET version, where it is hosted, and whether it faces the internet. Ask your vendor or in-house team for the target framework of each project, and for any Azure Functions apps on the in-process model.
- Rank by exposure. Put public-facing systems, payment flows and anything holding personal data first. Our legacy modernization assessment checklist gives a simple way to set the order.
- Check your dependencies. Confirm that the libraries, components and SDKs each system uses support .NET 10 before you schedule the work.
- Plan the move to .NET 10 with a test cycle. Review Microsoft's .NET 10 breaking changes list, run your regression tests, and use a staging environment or slot before switching production.
- Watch for silent changes in Functions apps. Microsoft's guide notes that the isolated model uses System.Text.Json by default, which ignores Newtonsoft.Json attributes such as JsonProperty without reporting an error. Test any data your functions read or write.
- Put upgrades into your support plan. .NET 10 support ends in November 2028, so the next deadline is already known. A software maintenance and support agreement can schedule framework upgrades as routine work.
Timeline Digital, a custom software development company founded in 2013 in Islamabad, builds business software as managed projects, including legacy software modernization that moves older systems onto supported platforms in planned stages, and maintenance and support after launch. Every project starts with a free pilot: Before you commit to the full project, we build 2 to 3 of your key modules as working software, free of charge, ready in about 2 days. Your team tests the pilot, and the full build starts only after you approve it.
Sources
- .NET 8 and .NET 9 will reach End of Support on November 10, 2026, .NET Blog, Microsoft, 29 June 2026
- .NET and .NET Core Support Policy, Microsoft, checked 10 November 2026
- .NET STS releases supported for 24 months, .NET Blog, Microsoft, 16 September 2025
- Migrate C# apps from in-process to isolated worker model, Microsoft Learn, updated September 2026
- Ending Support in 2026, Microsoft Lifecycle, checked 10 November 2026
- End of support looms for .NET 8 and .NET 9, InfoWorld, 1 July 2026