.NET 8 and 9 End of Support on 10 November 2026: What to Do

On 10 November 2026 (US time), support for .NET 8 and .NET 9, Microsoft's development platform, comes to an end. After that date, no fixes will be released even if new vulnerabilities are found. Support for PowerShell 7.4 and 7.5 ends on the same day.

This article is for companies that run in-house systems or business applications on .NET: how to check whether you are affected, where to move, and how to go about the migration, step by step. Systems you have left entirely to a development company are included.

Why do .NET 8 and .NET 9 end on the same day?

A new version of .NET comes out every November. Even-numbered versions are LTS (3 years), odd-numbered versions are STS (previously 18 months). Starting with .NET 9, Microsoft extended STS to 2 years, so .NET 8, released in 2023, and .NET 9, released in 2024, both end on the same date, 10 November 2026.

Companies that thought ".NET 9 is new, so we are fine for now" are affected too.

What problems does end of support cause?

Your applications will keep running after 10 November. The trouble is the problems found after that.

What is affected, and where to move

※ Dates are US time. Treat components that ship with .NET, such as ASP.NET Core and Entity Framework Core, as having the same deadline.

※ The next version, .NET 11, is STS and is still at the release candidate stage. For a system you will use for a long time, choosing .NET 10 first is the safe option.

Timeline

• 14 November 2023
  .NET 8 (LTS) released
• 12 November 2024
  .NET 9 (STS) released
• 11 November 2025
  .NET 10 (LTS) released
• 25 October 2026
  .NET 8.0.33 and 9.0.22 released. The last fixes within the support period
• 10 November 2026
  End of support for .NET 8 and .NET 9 (and for PowerShell 7.4 and 7.5)

How to check whether you are affected

First, list which of your systems run on .NET. You can check in the following ways.

• Check on the server: running dotnet --list-runtimes lists the .NET versions installed. If you see Microsoft.NETCore.App 8.0.x or 9.0.x, you are affected.
• Check in the source code: if <TargetFramework> in the project file (.csproj) is net8.0 or net9.0, you are affected.
• If you run in containers: check that you are not using 8.0 or 9.0 images such as mcr.microsoft.com/dotnet/aspnet:8.0.
• If .NET is bundled with the application (self-contained deployment): even if .NET is not installed on the server, .NET 8 or 9 is inside the application. It needs to be rebuilt and redistributed.
• PowerShell: $PSVersionTable.PSVersion shows the version. If it is 7.4 or 7.5, upgrade to 7.6.

Six steps to migrate

1. Make a list of your systems

   Using the methods above, write down every system running on .NET 8 or 9. Mark the ones that are open to the outside and the ones that handle personal data.

2. Decide the order

   Move the systems that are open to the internet first. Systems used only in-house can come after.

3. Change the version to .NET 10

   Change TargetFramework in the project file to net10.0, and also upgrade the components you use (NuGet packages) to their new versions.

4. Check for incompatible changes

   Review Microsoft's published list of "breaking changes" for both 9 and 10. If you are moving from .NET 8, the changes in .NET 9 in between apply too.

5. Run it in a test environment

   Check the main screens, reports, connections with outside systems, overnight processing and so on. If you have no automated tests, put the items to check into a table.

6. Switch production over and keep watch

   For a while after switching over, keep an eye on error logs and processing speed. Keeping the old environment for a short time, so you can roll back if something goes wrong, gives peace of mind.

If a development company looks after your system

Even if a development company looks after your system, the system belongs to your company. It is worth asking them:

• Which version of .NET does our system run on? Is it 8 or 9?
• What are your plans for moving to .NET 10, and roughly what cost and time frame?
• Are any of the components we use (NuGet packages) no longer being developed?
• Can we also receive the source code and the procedure for deploying to production?

If you can't reach your development company or no documentation remains, see "Taking Over a Legacy System With No Documentation". If you also have Java or PHP systems, see "Java Vulnerabilities, October 2026" and "What to Do About the PHP Vulnerability" as well.

Leave it, or migrate?

How Digi Dinos can help

Digi Dinos supports companies with DX, security, and system operations and maintenance. With offices in Japan and Vietnam, we have delivered more than 150 projects over 8 years. Our team works in Japanese.

• .NET migration: from checking versions to moving to .NET 10, testing and switching production over.
• Taking over maintenance of existing systems: we can take over systems built by other companies, in .NET, Java, PHP and more.
• Operations and monitoring after migration: we watch your servers and cloud 24 hours a day, 365 days a year, and can also apply the monthly fixes.
• No documentation? No problem: even when the original vendor is gone and nobody understands the system, we read the code, rebuild the documentation and propose a complete plan.
• Lifetime warranty: if a defect turns up in work we did, we fix it, with no time limit for as long as the maintenance contract continues.

Frequently asked questions