Action Required: Migrate to Windows Server 2022 by April 2026
As previously announced, Microsoft is retiring Windows Server 2019 support on Azure Kubernetes Service (AKS) enabled by Azure Arc (formerly AKS Hybrid on Azure Local releases after April 1, 2026. If you're running Windows Server 2019 workloads, you must migrate to Windows Server 2022 to maintain support, security updates, and the ability to upgrade Kubernetes versions.
Migration Approach
You cannot upgrade Windows node pools in place. The migration process requires:
- Creating new Windows Server 2022 node pools
- Updating and rebuilding container images with WS2022 base images
- Migrating workloads to the new pools
- Decommissioning old Windows Server 2019 pools
Make sure to allocate 2-4 weeks for testing, and plan to complete production migration by March 2026.
Key Milestones
| Milestone | Date | Details |
| Windows Server 2019 Support Ends | Post April 1, 2026 | No support or security updates after this date |
| Windows Server 2019 Retirement | Post April 1, 2026 | In new releases cannot create new node pools with WS2019 |
| Default Image Changes to WS2022 | Early 2026 | New deployments default to Windows Server 2022 |
Why Is This Happening?
- End of Mainstream Support: Windows Server 2019 mainstream support ended on January 9, 2024.
- Simplified Experience: Starting early 2026, Windows Server 2022 will be the default OS SKU, providing a seamless experience for new deployments.
What Happens After Retirement?
Immediate Impact on Your Clusters
Starting April 1, 2026, clusters still running Windows Server 2019 node pools will face the following restrictions:
Kubernetes Upgrade Blocking:
- Attempting to upgrade to Kubernetes versions (with Windows Server 2019 node pools) will be blocked
- Error message: "Windows Server 2019 images not available for the selected Kubernetes version. Please re-create your Windows node pool with a supported OS SKU"
Node Pool Creation Restrictions:
- Cannot create new Windows node pools with Windows Server 2019 OS SKU
Loss of Support:
- Support cases opened for clusters with Windows Server 2019 will require upgrade before assistance
- No security patches or updates will be available
- Clusters will be considered out of compliance
Default Image Transition (Early 2026)
Starting in early 2026, Windows Server 2022 will become the default OS SKU for all new Windows node pool deployments created on the clusters on the latest Azure Local releases.
This change ensures new deployments automatically use the supported OS version, reducing the risk of accidentally deploying deprecated images.
Getting Started
For detailed step-by-step instructions, see our Migration How-to Guide, which includes:
- Commands to identify affected clusters
- Container image update procedures
- Node pool creation and workload migration steps
- Validation and troubleshooting guidance
Frequently Asked Questions
General Questions
Q: What happens if I don't upgrade before the retirement date?
A: After April 2026, your clusters running Windows Server 2019 will lose support. You will be required to upgrade before receiving any assistance from Microsoft support. Your clusters will also be unable to upgrade to Kubernetes versions, potentially leaving them on unsupported Kubernetes releases.
Q: Can I upgrade my Windows node pools in place?
A: No. Windows node pools cannot be upgraded in place. You must create new node pools with Windows Server 2022, migrate your workloads, and then decommission the old node pools.
Q: Will my existing container images work on Windows Server 2022?
A: Most Windows Server 2019 container images will work on Windows Server 2022 hosts. However, we recommend rebuilding your images on the Windows Server 2022 base for optimal performance, security, and compatibility.
Q: Can I upgrade my Kubernetes version with Windows Server 2019 node pools still running?
A: No. Upgrades to Kubernetes versions will be blocked if you have any Windows Server 2019 node pools in your cluster. You must migrate to Windows Server 2022 first.
Migration Questions
Q: How long does a typical migration take?
A: Migration time varies based on the number of applications, complexity, and data volume. Simple applications may migrate in hours, while complex environments may take days or weeks. Plan for adequate testing time.
Q: Can I run Windows Server 2019 and Windows Server 2022 node pools in the same cluster?
A: Yes, during the migration period you can have node pools with different OS SKUs in the same cluster. This enables gradual migration and testing.
Q: Will there be any downtime during migration?
A: Downtime depends on your migration strategy. For stateless applications using rolling updates, downtime can be minimal or zero. Stateful applications may require planned maintenance windows.
Additional Resources:
Microsoft