FEAT(Post): adds blogpost for .NET EOL

docs/_posts/2026-09-16-.net8-eol-and-IdentityServer.md

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+---
+title: ".NET 8 Reaches End of Life: Is Your Sitecore Identity Server Ready?"
+date: 2026-09-16 10:00:00 +0100
+categories:
+- Sitecore
+tags:
+- Sitecore
+- Sitecore XP
+- OnPremise
+- Identity Server
+- .NET
+author: hlueneburg
+---
+![alt text](../files/2026/09/16/net8eoltitle.jpg "Tombstone for .NET 8")
+
+Are you aware that .NET 8 will reach its end of life on November 10, 2026?
+
+If you are running a Sitecore solution, this is something you should pay attention to. Sitecore Identity Server 8.x is built on .NET 8 and cannot simply be moved to newer .NET versions such as .NET 10.
+
+If your infrastructure administrators actively manage runtime lifecycles and remove unsupported frameworks, you could unexpectedly lose authentication functionality after .NET 8 reaches EOL.
+
+## Initial Situation
+
+One of our infrastructure administrators recently approached me regarding the upcoming end of support for .NET 8.
+
+My initial reaction was simple:
+
+> "The Identity Server probably runs on .NET 10 without any issues. Let's verify it in a test environment."
+
+After some testing, the result was clear:
+
+Sitecore Identity Server 8.x is not compatible with .NET 10.
+
+## Sitecore Identity Server 8.x
+
+Sitecore Identity Server 8.x is based on .NET 8 and supports Sitecore XP versions 9.1 through 10.4.
+
+For example, see the release information for [Sitecore Identity Server 8.0.37](https://developers.sitecore.com/downloads/Sitecore_Identity/8x/Sitecore_Identity_Server_8037).
+
+If you are running one of these Sitecore versions, verify which Identity Server version is deployed in your environment and whether your infrastructure team has plans to remove unsupported .NET runtimes after November 2026.
+
+## Sitecore Identity Server 9.x
+
+Sitecore released Identity Server 9.0.7 shortly before the release of Sitecore XP 10.5.
+
+It supports Sitecore XP versions 10.3 through 10.5 and is based on a newer runtime stack. For details, see [Sitecore Identity Server 9.0.7](https://developers.sitecore.com/downloads/Sitecore_Identity/9x/Sitecore_Identity_Server_9007).
+
+For organizations running Sitecore XP 10.3 or newer, upgrading the Identity Server may be an option to address the .NET 8 end-of-life situation.
+
+## Conclusion
+
+The upcoming end of support for .NET 8 is more than just a routine runtime upgrade consideration. For Sitecore solutions, it may directly impact your authentication infrastructure.
+
+Now is a good time to:
+
+- Review the Identity Server version running in your environments.
+- Verify its runtime dependencies.
+- Align upgrade plans with your infrastructure and security teams.
+- Evaluate whether an upgrade to Identity Server 9.x is possible for your Sitecore version.
+
+Do not wait until November 2026 to discover that a critical component of your Sitecore platform depends on an unsupported .NET runtime.