SharePoint Embedded

Office Online Server End of Support: Your Options for Browser-Based Office Editing

Office Online Server End of Support: Your Options for Browser-Based Office Editing

Microsoft is retiring Office Online Server (OOS). Its announcement is short and unambiguous: “Microsoft is announcing the end of support and retirement for Office Online Server effective December 31, 2026. After this date, Office Online Server will no longer receive security updates, bug fixes, or technical support from Microsoft.”

For a decade, OOS has been the on-premises engine behind browser-based Word, Excel and PowerPoint in SharePoint Server and Exchange Server. In Microsoft’s words, it “works with products and services that support WOPI, the Web app Open Platform Interface protocol. These products, known as hosts, include SharePoint Server, and Exchange Server.” When support ends, every one of those hosts needs a plan.

This article covers the Office Online Server end of support in practical terms: what stops working, what Microsoft recommends, how to find every system that depends on your OOS farm, and the main Office Online Server alternatives. That includes the option Microsoft names for custom applications, SharePoint Embedded. Every fact about Microsoft’s products comes from Microsoft’s own posts and documentation, checked on 9 October 2026 and listed at the end. The option analysis and decision tree are ours.

What Changes on 31 December 2026

Microsoft’s lifecycle listing for OOS records it under the Modern Lifecycle Policy, with a retirement date shown as 1/1/2027 6:59:59 AM (the page gives support dates in US Pacific time). The retirement announcement gives the date as December 31, 2026. After that date there are no more security updates, bug fixes or support.

Microsoft’s product teams have described the practical effect on each host.

SharePoint Server. The SharePoint team’s announcement states that without OOS, “Users will lose the ability to view, edit, and collaborate on Office documents directly in the browser. Office client applications can still be used to view and edit Office documents.” It also covers previews: “SharePoint Server relies on OOS to generate previews for Word, Excel, PowerPoint, and PDF documents. After OOS support ends, these thumbnails will no longer be actively supported in libraries and search results.”

Two further lines from that announcement matter for planning:

  • “Office Online Server will not be supported in any configuration after retirement, including scenarios where it is paired with SharePoint Server Subscription Edition.”
  • “Microsoft will not actively block the use of OOS in SharePoint Server after its retirement.”

Exchange Server. The Exchange team lists two OOS-dependent features: “Previewing Office file types in OWA” and “Live edit capabilities in OWA”. After retirement, “on-premises users will need to first download the attachments to view / work with them. Exchange Online users will continue to be able to work with attachments using Outlook on the web since OOS is not being used in the cloud.”

Power BI Report Server. “If your organization uses Office Online Server to host Excel workbooks in Power BI Report Server, that functionality will no longer be supported. Alternatives include viewing workbooks in the Excel desktop application or migrating to the Power BI service.”

Microsoft’s Position

The retirement announcement sets out Microsoft’s recommendations:

  1. Microsoft 365 is the recommended path. “Our recommended path is to transition to Microsoft 365, which includes cloud-powered versions of Word, Excel, PowerPoint, and OneNote.”
  2. SharePoint Embedded for custom applications. “SharePoint Embedded enables real-time collaboration on Word, Excel, and PowerPoint documents directly within line-of-business or custom applications using Microsoft 365’s native co-authoring services.”
  3. Desktop clients for Subscription Edition servers. “For organizations using SharePoint Server Subscription Edition or Exchange Server Subscription Edition, Microsoft 365 Apps for Enterprise and Office LTSC 2024 remain supported desktop clients for viewing and editing documents hosted on those servers.”

It is notable that Microsoft’s own retirement notice names SharePoint Embedded. For organisations that pointed a custom or line-of-business application at OOS, this is, in our reading, the clearest statement yet from Microsoft about where that workload should go.

Step 1: Inventory Everything That Points at Your OOS Farm

You cannot plan a retirement until you know what depends on the farm. These checks use cmdlets from Microsoft’s documentation.

On the OOS farm itself:

  • Get-OfficeWebAppsFarm “Returns details about the OfficeWebAppsFarm object that the current server is a member of.”
  • Get-OfficeWebAppsMachine returns “the roles and health status of the current server and the name of the master server for the farm.”
  • Get-OfficeWebAppsHost “Returns the list of host domains that are on the Allow List for an Office Online Server farm.” This is the most useful starting point. Every domain on that list is a host that may depend on the farm. If the list is empty, Microsoft notes that Office Online Server “allows file requests to hosts in any domain”, so the list cannot tell you which hosts depend on the farm. In that case, rely on the SharePoint and Exchange checks below and on the owners of your custom applications.

On each SharePoint Server farm:

  • Get-SPWOPIBinding “Returns a list of bindings that were created by using New-SPWOPIBinding”. The results “include actions, applications, file types and zones that are configured for a WOPI application”.
  • Get-SPWOPIZone returns the zone in use: “internal-http,” “internal-https,” “external-http” or “external-https.”
  • Check whether the farm relies on the Excel SOAP API, which Microsoft notes “is needed for scheduled data refresh with Excel Online, and for Excel Web Part rendering”.

On each Exchange Server organisation:

  • The WacDiscoveryEndpoint setting, at organisation level (Set-OrganizationConfig) or per server (Set-MailboxServer), “specifies the discovery endpoint for Office Online Server”. Read the current values with the matching Get- cmdlets.

Custom WOPI hosts. This is our addition. If any domain on the OOS allow list is not a SharePoint or Exchange server, treat it as a custom or third-party WOPI host and find its owner. Those applications are the ones most likely to have been forgotten, and they have no Microsoft-supplied replacement inside the product.

The output of this step should be a simple register: each host, its owner, what it uses OOS for (editing, viewing, previews, Excel web parts, OWA attachments), how many users depend on it, and which option below it will move to.

Step 2: Choose an Option per Host

This is our analysis of the main options. Most organisations will use more than one.

Option 1: Microsoft 365 for internal collaboration

Best for: intranet and team collaboration on SharePoint Server, and on-premises mailboxes.

This is Microsoft’s recommended path and the most complete replacement. Office for the web, co-authoring and previews come with the service. Exchange Online users “will continue to be able to work with attachments using Outlook on the web since OOS is not being used in the cloud.” The cost is the migration itself: content, permissions, customisations and the change for users. That is a programme, not a quarter’s work, so start it now even if it will not finish by 31 December.

Option 2: Stay on Subscription Edition, with desktop editing

Best for: organisations that must keep SharePoint Server or Exchange Server on-premises.

Microsoft 365 Apps for Enterprise and Office LTSC 2024 “remain supported desktop clients” for documents on SharePoint Server SE and Exchange Server SE. The SharePoint team adds that Microsoft is “committed to supporting SharePoint Server Subscription Edition until at least December 31, 2035.” Users lose browser editing and, on SharePoint, actively supported Office thumbnails. Exchange users download attachments to open them. For some organisations that is acceptable. For others it is a significant change, so test it with real users before you commit.

Option 3: SharePoint Embedded for custom and line-of-business applications

Best for: applications you build or buy that currently embed OOS through WOPI.

SharePoint Embedded is “a cloud-based, API-only file and document management system you can use in any application.” Microsoft’s documentation highlights several properties that matter here:

  • “Real-time co-authoring in Office for the web and Office desktop clients.”
  • “No per-seat license required for end users”. Billing is pay-as-you-go through Azure, “based on storage and API usage”.
  • It is presented as a way to stop running a WOPI host at all: “If you already integrate Office through a… (WOPI) host, you can keep files in SharePoint Embedded and move to the built-in Office launch patterns instead of maintaining your own host.”

One design difference must be planned for. “Office for the web isn’t iframeable today.” Office for the web “opens in a new browser tab or window”. To keep users inside your application, Microsoft recommends embedding “a read-only file preview, which is designed to render in an iframe”, using the Microsoft Graph driveItem preview endpoint. An application that currently shows an OOS editor inside its own page will move to the pattern Microsoft describes: “Use the Office launch patterns for editing, and use preview for inline viewing.” That is a user experience change to design deliberately, not discover at testing.

Files move to Microsoft 365, so SharePoint Embedded is a cloud option. It is not a like-for-like replacement for an organisation that adopted OOS specifically to keep documents on-premises. We have written about the architecture in What Is SharePoint Embedded? and about the move from a WOPI host in Migrating from a Custom WOPI Host to SharePoint Embedded: A Practical Playbook.

Option 4: The Cloud Storage Partner Program, for storage software vendors

Best for: software vendors whose product includes cloud file storage and who embedded OOS for their customers.

The Microsoft 365 Cloud Storage Partner Program (CSPP) lets an eligible vendor connect its WOPI host to Microsoft 365 for the web instead of OOS. The criteria are strict. The programme is “not open to Microsoft 365 customers directly”; files must be stored at rest “in a cloud location entirely owned or leased by the partner”; the vendor must serve “more than one external customer”; and “Any user who will edit files using a Microsoft 365 app must have a valid Microsoft 365 license.” Your existing WOPI host is a head start, but the route to production includes an eligibility review, validation by the CSPP team, and two environment configuration changes that Microsoft says “typically take 4-5 weeks each”. Read more about the programme on our CSPP and WOPI services page.

Option 5: A self-hosted editor, where documents must stay on-premises

Best for: applications, especially Word-centred ones, that cannot move documents to the cloud.

Some organisations adopted OOS precisely because documents could not leave their infrastructure. Neither Microsoft 365 nor SharePoint Embedded keeps documents on-premises, and CSPP requires the partner’s own cloud storage. For those organisations, a self-hosted, browser-based editor is the remaining route to browser editing.

For Word-centred applications, SuperDoc is one example. It describes itself as “an open source DOCX Editor and Agent SDK for adding DOCX editing into web apps and agents”, and its documentation states: “Your documents stay on your infrastructure.” Its website states that it can run “in your cloud, private network, or on-premises environment, including deployments without public internet access.”

The limits are important. SuperDoc is a Word (DOCX) editor, not Microsoft’s editor, and it does not replace Excel or PowerPoint editing. You also run more of the stack yourself, including collaboration infrastructure if you need co-editing. We compare it with Microsoft’s options in How Does SuperDoc v2 Compare to CSPP WOPI?

If Excel or PowerPoint editing must also stay on-premises, look at self-hosted office suites instead: ONLYOFFICE Docs can be hosted “on your own server”, includes spreadsheet and presentation editing, and has supported WOPI since version 6.4, while Collabora Online “supports all major document, spreadsheet and presentation file formats”, works “in any modern browser” and is a suite “which you can integrate into your own infrastructure”.

Not an option: running OOS unsupported

Microsoft “will not actively block” OOS in SharePoint Server after retirement. That is not the same as support. Our view is clear: a server component that renders untrusted documents and receives no security updates becomes a growing liability from 1 January 2027. If a host cannot move by then, treat continued use as a documented, time-limited risk exception with compensating controls and an owner. It is not a plan.

A Decision Tree

Run each host in your register through these questions, in order.

  1. Is it SharePoint Server or Exchange Server used for internal collaboration?
    • If the organisation can move to the cloud: Microsoft 365 (Option 1).
    • If it must stay on-premises: Subscription Edition with desktop clients (Option 2), and test the loss of browser editing and previews with users.
  2. Is it a custom or line-of-business application that embeds OOS?
    • If documents can live in Microsoft 365: SharePoint Embedded (Option 3).
    • If documents must stay on-premises and the need is mainly Word: a self-hosted DOCX editor (Option 5).
    • If documents must stay on-premises and Excel or PowerPoint editing is essential: Microsoft names no on-premises browser editor to replace OOS. Plan for desktop editing or evaluate a self-hosted office suite (Option 5), and review the requirement.
  3. Is it a software product sold to external customers, with its own cloud storage?
    • If you meet the criteria: CSPP (Option 4).
    • If not: SharePoint Embedded (Option 3) or a self-hosted DOCX editor (Option 5).
  4. Is it Excel workbooks in Power BI Report Server? Use Microsoft’s stated alternatives: Excel desktop or the Power BI service.

Step 3: Plan the Disconnection

For each host you migrate, finish with a clean disconnection rather than simply switching the farm off.

  • SharePoint Server. Microsoft’s guidance for disconnecting a farm is Remove-SPWOPIBinding -All:$true. The cmdlet reference warns that once all bindings are removed, “users cannot use Office Web Apps or the SharePoint Share by link feature for any applications in the SharePoint library”. Communicate the change first.
  • Exchange Server. Remove the WacDiscoveryEndpoint configuration at organisation and server level. Microsoft’s installation guidance restarts the OWA application pool (Restart-WebAppPool MsExchangeOwaAppPool) after changing this setting; plan for the same when you remove it.
  • Custom hosts. Remove the host from the OOS allow list only after its replacement is live, and keep the register updated until the last host has moved.

With the end of support in a little over ten weeks from the date of this article, our recommendation is to complete the inventory now, decide each host’s option before the end of November, and be clear which hosts will still be on OOS on 1 January and why.

How McKenna Consultants Can Help

McKenna Consultants is a UK WOPI integration consultancy that has built browser-based Office editing into software products for years. We delivered WOPI architecture for Kendox, whose document platform serves both SaaS and on-premises customers, and a clustered PHP WOPI implementation for Corcentric. We also build on SharePoint Embedded and work with self-hosted DOCX editors, so we can advise on every option above rather than just one.

We can run your OOS inventory, design the replacement for each custom application, migrate a WOPI integration to SharePoint Embedded or CSPP, or plan a self-hosted editor where documents must stay in your infrastructure. Contact us to talk through your OOS estate, or read more about our SharePoint Embedded and WOPI services.

Sources

All sources checked on 9 October 2026.

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