On 12 January 2027, Microsoft will ship the last security update for Windows Server 2016. After that, every newly discovered vulnerability stays open. Many SMEs still run this exact version: as a domain controller, file server, terminal server or as the base for their ERP.
That leaves a little under three months. Enough for a planned migration, provided you start now.
Why this is more urgent than it looks
Windows Server 2016 rarely comes alone. Other products of a similar age often depend on it, and their support has already ended:
- SQL Server 2016 has received no updates since 14 July 2026. Many industry applications use exactly this database.
- Exchange Server 2016 and 2019 have been out of support since 14 October 2025. An on premises mail server of this generation is reachable from the internet and therefore particularly exposed.
- Office 2016 and 2019 on the terminal server have also been unsupported since October 2025.
- Windows Server 2012 and 2012 R2 reached their final end on 13 October 2026, even with paid Extended Security Updates (ESU).
So a Server 2016 still in service often hides several problems on one machine.
The catch with SQL Server 2016
One point is easily missed during planning: Microsoft does not support SQL Server 2016 on Windows Server 2022 or 2025. Upgrading the operating system alone is not enough if the database moves along. The SQL version has to be upgraded too, which usually needs the approval of the software vendor.
So start by asking the vendor of your business software which Windows and SQL versions they support for the current release of their product.
How to proceed
- Take stock. Which servers run which version, and which services and programs are installed on them? Do not forget virtual machines that were set up for a single purpose years ago.
- Clarify dependencies. ERP, accounting, time tracking and print management all have their own requirements. Get the vendors’ approval in writing.
- Choose the target version. For new installations we recommend Windows Server 2025. Check your licences as well: Server CALs for version 2016 do not cover access to a 2025 server.
- Reinstall rather than upgrade. A fresh server with cleanly migrated roles and data runs more reliably than an in place upgrade across two versions.
- Plan the cutover. Domain controller, file storage and applications can be moved step by step. The actual switch usually happens in an evening or over a weekend.
What if January comes too soon?
Microsoft offers paid Extended Security Updates for Windows Server 2016. They are charged per core and year and become more expensive each year. As a bridge for a single server whose software is not yet approved, this can make sense. As a permanent solution, it does not pay off.
Important: a server without updates must never be directly reachable from the internet. If the replacement takes longer, put it in its own isolated network segment at the very least. Our article on securing the company network shows how.
What we take care of
We take the inventory, talk to your software vendors and plan the migration so that your business keeps running. Whether the new server runs on your own hardware, on Proxmox or in a Swiss data centre is something we decide together. More under Servers & virtualisation.
Frequently asked questions
Does the server keep running after 12 January 2027?
Yes. It starts and works as before, but no longer receives security updates. The risk grows every month as new vulnerabilities become known and remain open.
Can we upgrade directly from 2016 to 2025?
A direct upgrade is technically possible. We still usually recommend a fresh installation, because a lot of clutter has built up over the years and the migration is easier to plan that way.
How long does a server migration take in an SME?
For a company with one to three servers, expect two to four weeks from inventory to cutover. The longest wait is often the approval from the software vendor.
What happens to our on premises Exchange server?
Exchange 2016 and 2019 already receive no more updates. Options include Exchange Server Subscription Edition, a move to Microsoft 365 or another mail system such as Zimbra. We show you the pros and cons for your situation.
