When support for your .NET version ends: what it means and what to do

The dates that matter

Source: Microsoft's support policies for .NET and for .NET Framework (see Sources).

What the end of support means in practice

Nothing switches off on the day. The application keeps running, and the runtime can still be installed. What stops is the flow of fixes: a vulnerability found afterwards in the runtime or the framework libraries stays open. Over the following months the effects add up:

• vulnerability scanners and dependency checks flag the runtime on every run;
• security questionnaires, customer audits and cyber-insurance forms ask whether your software is supported, and the honest answer becomes "no";
• libraries and container images drop the old version, so updating anything else gets harder;
• each month of delay adds changes to the eventual upgrade.

How .NET support works

Microsoft releases a new version of .NET every November. In its own words, "LTS releases get free support and patches for three years. STS releases get free support and patches for two years." Microsoft lengthened standard-term support to two years starting with .NET 9, which is why .NET 8 and .NET 9 end on the same day. For a business application that is upgraded every few years, the current LTS release is the steadier target.

Check your exposure in an hour

1. List every application, service, function and scheduled job, with its target framework (net8.0, net9.0).
2. Check what runs in production: installed runtimes on servers and the base images of your containers.
3. Check the build: the SDK version in global.json and on build agents.
4. List third-party packages that are pinned to old versions or that have not yet released a version for .NET 10.
5. Mark anything that faces the internet or handles payments and personal data: it moves first.

Moving from .NET 8 or 9 to .NET 10

For most applications this is a contained piece of work:

1. Update the SDK and change the target framework to net10.0.
2. Update Microsoft and third-party packages to their .NET 10 versions.
3. Read Microsoft's list of breaking changes for .NET 10 and check each one that touches your code.
4. Run the test suite, then test the parts it does not cover, by hand or with new tests.
5. Update container base images and hosting settings, deploy to a test environment, then to production with a way back.

The risk sits in what the tests do not cover, not in the version number. That is where to spend the review time.

Still on .NET Framework?

That is a different project: the application moves to modern .NET, not between two versions of it. The step-by-step guide covers it, and the hard parts cover WebForms and WCF.

Questions people ask

1. 01

   Will our application stop working when support ends?

   No. It keeps running; it just receives no security fixes after 10 November 2026.

2. 02

   Should we skip .NET 10 and wait for a newer release?

   For most business applications, no: .NET 10 is the long-term-support release with the longest runway, until 14 November 2028.

3. 03

   How long does a move from .NET 8 to .NET 10 take?

   It depends on test coverage, the number of services and the third-party packages involved. It is usually far smaller than a migration from .NET Framework, and a short review can size it precisely.