Definition
What does modernizing SharePoint Server 2016 and 2019 mean?
Modernization for SharePoint Server 2016 and 2019 is the move from a .NET Framework application that no longer receives vendor fixes to a platform that does, without losing the data, users, integrations and business rules that took years to build.
In practice it is three projects at once: build the new system, keep the old one running, and make the switch between them reversible.
Most modernization guidance covers the first project. Jestr covers the other two. A live replica of the legacy SharePoint Server application is a clean, current reference to build against, a fallback that users can be switched to in seconds if the new platform fails, and a way to keep an unsupported application running without leaving it exposed on the internet.
Why now
Why SharePoint Server modernization stopped being optional on July 14, 2026
Most organizations planned to be off SharePoint 2016 and 2019 before July 14, 2026. Most are not, because the migration is never just content: custom web parts, workflows, InfoPath forms and years of permission sprawl all have to be reconsidered. The farm stays running, unpatched and holding the documents, while the program catches up.
The facts driving the decision for SharePoint Server 2016 and 2019 today:
- Extended support for SharePoint Server 2016 and SharePoint Server 2019 ended on July 14, 2026. Mainstream support ended in July 2021 and January 2024 respectively.
- After that date Microsoft provides no security fixes, no assisted support and no technical content updates for either version.
- SharePoint Server Subscription Edition is the only supported on-premises version, and Microsoft's investment is in SharePoint Online and Microsoft 365.
- SharePoint has been a repeated target of actively exploited vulnerabilities, including the ToolShell chain in 2025 that hit on-premises servers worldwide.
Migration risks
The risks of a rip-and-replace SharePoint Server migration
The classic modernization plan is a big-bang cutover: build the new application, freeze the old one, migrate the data over a weekend, switch the DNS, and hope. It fails in predictable ways.
- The migration runs long. Business rules, integrations, authentication and reporting never map cleanly. The legacy application stays in production, exposed and under-maintained, for months longer than planned.
- The cutover is one-way. Once users are on the new platform and new data are flowing, going back means losing them. Teams push through launch-day failures they should have rolled back from.
- The reference disappears. The legacy application is frozen or decommissioned to save cost, and the next question about how a workflow used to behave has no answer.
- SEO and users trust take the hit. Users lose access to the tool they know on the day the new one has its worst bugs.
- The legacy application gets breached mid-migration. An unpatched, half-forgotten production system is the softest target in the estate, and a compromise during the program can stop it cold.
The replica
How the Jestr replica de-risks a SharePoint Server migration
The replica does not build the new platform. It makes the migration survivable.
A clean reference the rebuild can trust
The replica is a current, working copy of the legacy SharePoint Server application, isolated from the change and churn of production. Developers and QA compare behavior against it, test data migrations against it and answer "how did this work before?" without touching production.
A cutover you can reverse in seconds
Launch the new platform with the replica standing by. If checkout, logins or integrations fail on day one, users switch back to the replica while the team fixes the problem. Changes made on the replica are reconciled afterwards. The launch stops being a bet.
Run past end of life without running exposed
SharePoint Server 2016 and 2019 will not receive another vendor fix. The replica lets you shrink what is exposed: restrict or retire the internet-facing primary early and keep the isolated replica as the working copy while the migration finishes, however long it takes.
Retire the old infrastructure earlier
With the replica as the safety net, the legacy servers, licenses and domain trusts can be wound down on a schedule the finance team likes rather than after a year of "just in case".
How it works
How the replica fits a SharePoint Server modernization program
Jestr does not re-implement SharePoint Server 2016 and 2019. It runs a copy of your actual application, kept current and kept apart, for as long as the program needs it.
Jestr builds a live copy of the legacy SharePoint Server application
Jestr replicates the application as it actually runs: application, data and configuration at the exact .NET Framework version and dependencies the primary uses. Nothing is re-implemented, so the replica behaves like the application the business knows.
The copy stays current and isolated while you build
The replica follows the primary continuously at a known-good state. It runs on Jestr's side with no shared credentials, network or identity, so it is both a faithful reference and a safe one.
At cutover, the replica stands by
Users move to the new platform. If it fails, one action moves them back to the replica. Changes made there are captured and reconciled when the new platform is stable.
After cutover, the replica is the legacy system
The exposed primary can be decommissioned. The replica stays as the working reference and fallback for as long as the program needs it, then it is retired too.
SS What the replica preserves from SharePoint Server 2016 and 2019
- Site collections, libraries, lists, documents and the content databases behind them, so the intranet and document stores are intact on the replica.
- Search, permissions and authentication, so people can find and open what they need rather than browse a frozen copy.
- Custom solutions and workflows at a known-good state, kept current with the primary.
- Isolation from the primary's domain, network and credentials, so ransomware in the estate has no path to the copy.
Destinations
Where SharePoint Server applications usually go
The destination depends on how much of the business lives in SharePoint Server customizations. Common paths from SharePoint Server 2016 and 2019:
- SharePoint Online and Microsoft 365, with custom solutions rebuilt in Power Platform or SPFx.
- SharePoint Server Subscription Edition for workloads that must stay on-premises.
- A phased move with the legacy farm kept live and isolated until the last workload leaves.
Side by side
Rip and replace vs a parallel SharePoint Server replica
The same migration, run two ways.
| Dimension | Rip and replace | Live Jestr replica |
|---|---|---|
| Legacy system during the migration | Exposed in production, under-maintained, single copy | Primary can be restricted early; the isolated replica is the working copy |
| Cutover | One-way; rolling back loses data | Reversible in seconds; changes on the replica are reconciled |
| Reference for the rebuild | Production, which keeps changing, or a stale staging copy | A current, isolated, working copy of the legacy application |
| Running past end of life | Every new vulnerability is permanent and the only copy is exposed | Exposure shrinks to what is strictly needed; the replica carries the rest |
| Timeline pressure | Every delay extends the exposed window | Delays are safe; the migration finishes when it is right |
| Decommissioning | Kept running for months as insurance | Retired on schedule; the replica is the insurance |
FAQ
Frequently asked questions
Can we keep running SharePoint Server 2016 and 2019 after end of extended support?
Yes, and most teams will. The safe way is to reduce exposure rather than pretend the software is patched: keep the Jestr replica live and isolated so a compromise of the primary is contained, restrict the primary to what strictly needs it, and use the replica as the fallback at every migration milestone.
What happens if the new platform fails at cutover?
Users are switched back to the replica in seconds. It is current and running, so there is no restore. Changes made on the replica while the team fixes the new platform are captured and reconciled afterwards. Launch day becomes something you can retry.
How does the replica stay current during a long migration?
It follows the primary continuously at a known-good state, so data, configuration and integrations stay in sync until the day you freeze them for the final data migration. At that point the replica is the frozen reference the migration is validated against.
Does the replica preserve our SharePoint Server customizations and historical data?
Yes. The replica is a copy of the application as it runs, including extensions, custom code, configuration and data. It is not a re-implementation, so nothing has to be ported to it.
When can we retire the replica?
When the new platform has run long enough that nobody would switch back, and the legacy application is no longer needed as a reference. Many teams keep it through the first full business cycle on the new platform and retire it after.