SharePoint deadline

Office Online Server retirement: what SharePoint Server farms lose on December 31, 2026

By the MMM team — November 7, 2026

The Office Online Server retirement takes effect on December 31, 2026. From then on, Microsoft ships no security updates, bug fixes or technical support for the server that lets SharePoint Server open Word, Excel and PowerPoint files in the browser, lets people co-author them there and draws document previews in libraries and search. Exchange Server and Power BI Report Server lean on it too.

This is not the same change as the SharePoint Server mobile app retirement on November 27, 2026. That one ends access to the farm from the SharePoint apps on iOS and Android. This one ends supported browser viewing, editing and co-authoring of Office files on every device, desk included. The audience is the same, organizations still running a farm, but the broken capability and the fix are different. Every Microsoft statement below was checked against Microsoft’s published announcements and documentation on November 7, 2026.

What changes on December 31, 2026?

From December 31, 2026, Microsoft stops shipping security updates, bug fixes and technical support for Office Online Server. Microsoft will not actively block it, but SharePoint Server’s browser viewing, editing and co-authoring of Office files, and its document previews, depend on it and lose support. Exchange Server and Power BI Report Server integrations are affected too.

Microsoft announced the date on its Office end-of-support blog on October 21, 2025, and the SharePoint team set out the farm-side consequences on November 12, 2025. No on-premises successor was announced. Here is what each integration loses:

The dates are on Microsoft’s Office Online Server lifecycle page (opens in new tab), which shows the product under the Modern Lifecycle Policy with a retirement date at the end of 2026, Pacific time. There is no extended security update program on that page, so plan as if the last patch has already shipped.

Who is affected by the retirement?

Any organization that runs SharePoint Server, Exchange Server or Power BI Report Server on-premises with an Office Online Server farm connected to it. If users click a Word or Excel file in a SharePoint Server library and it opens in the browser, or preview attachments in Outlook on the web against your own Exchange, you are affected.

Microsoft 365 tenants are not. SharePoint Online and Exchange Online use Office for the web, which Microsoft runs inside Microsoft 365. Hybrid organizations feel the change unevenly: a file in OneDrive or an Online site still opens in the browser, while the same kind of file on the farm opens in a desktop app, or not at all on a machine without one. That second group, shared PCs, kiosks and contractors without an Office install, is the one most likely to lose access outright.

Can you keep Office Online Server running after the date?

Technically yes, since Microsoft says it will not actively block it. Practically, it becomes an unpatched server that opens every document your users view in the browser. That is acceptable only as a short, documented bridge while you roll out desktop apps or plan a move to Microsoft 365, not as a permanent state.

Office Online Server parses whatever file a user clicks, from any library it can reach. A flaw found in that code after December 31 stays open for good. If you do run it past the date, keep it off the internet, limit it to the farms that still need it, and write down when it will be switched off.

Which options does a farm have?

Three supported directions, plus a stopgap. Keep the farm and send users to Microsoft 365 Apps or Office LTSC 2024 on the desktop; move the collaboration-heavy sites to SharePoint Online, where Office for the web keeps working; or move everything. Running Office Online Server unpatched is the stopgap, not an option.

The co-authoring gap deserves a plain test before you choose the desktop route. Microsoft’s Excel co-authoring article (opens in new tab) lists OneDrive and SharePoint Online libraries as the supported locations and says on-premises SharePoint sites do not support co-authoring. Any team that edits one workbook together today will notice on the first working day of January. Line-of-business applications that embedded Office Online Server have a different route: Microsoft points them to SharePoint Embedded.

What should admins do before December 31, 2026?

Find out what actually uses the Office Online Server farm, tell users how they will open files after the date, check that supported desktop apps are deployed to everyone who needs them, and put the farm’s longer-term future on the agenda now.

1. Map the bindings. List every SharePoint Server farm, Exchange Server and Power BI Report Server connected to Office Online Server. Farms are often bound years ago and forgotten.
2. Find who edits in the browser. Site owners and the help desk know which teams co-author workbooks or work from machines without Office installed.
3. Check the desktop estate. Confirm Microsoft 365 Apps for enterprise or Office LTSC 2024 is on every machine that will open farm documents.
4. Send one clear notice. Say what changes, on which date, and how files will open instead. Warn Excel teams that simultaneous editing on the farm ends.
5. Set an end date for the server. If it stays up as a bridge, decide now when it comes down and who signs that off.

Does this make moving to SharePoint Online urgent?

It moves the question up the list. Desktop apps cover opening and editing, so a farm can carry on. What it cannot get back on-premises is supported browser editing and Excel co-authoring. Combined with this month’s mobile app change, browser and app collaboration now live in Microsoft 365, and that belongs in your stay-or-go decision.

If the decision is still open, weigh it with our SharePoint Online vs on-premises comparison, which sets out when a farm still earns its keep. If you have already decided to move, the SharePoint Server to SharePoint Online migration page describes how we plan and run it, and a first wave can be just the sites where people co-author most.

Either way, our SharePoint consulting work is scoped and priced before anything starts, delivered by senior US-based Microsoft engineers, typically within 2–4 weeks, with 30 days of hypercare afterwards. We are based in Orange County, California, and work with businesses across the US remotely. See how the fixed-fee process works.