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Exchange Team Blog
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Retirement Date for Office Online Server (OOS) has been Announced

The_Exchange_Team's avatar
The_Exchange_Team
Platinum Contributor
Oct 21, 2025

We want to let our Exchange Server customers know that the Office Online Server (OOS) team has announced product retirement on December 31, 2026: Announcing the retirement for Office Online Server.

Office Online Server is an optional component that can be integrated with Exchange Server on-premises and it provides the ability to work with supported types of file attachments within Outlook on the web without having to download them, first.

The following actions in Exchange Server make use of Office Online Server:

  • Previewing Office file types in OWA
  • Live edit capabilities in OWA

Microsoft will not actively block usage of OOS in Exchange Server after its retirement. However, it's no longer maintained, and no further (security) updates will be provided.

After Office Online Server 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.

For more information, please see Announcing the retirement for Office Online Server.

The Exchange Team

Updated Oct 21, 2025
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5 Comments

  • evandromalmsteen's avatar
    evandromalmsteen
    Brass Contributor
    Nov 03, 2025

    Retiring Office Online Server by 12/31/2026 is a mistake — and there is a better path.

    Ending support for Office Online Server (OOS) pushes everyone to Microsoft 365/Office for the Web and leaves on-prem customers (regulatory, data-sovereignty, disconnected) without a supported way to preview, edit, and co-author documents locally. There are concrete impacts already called out, such as Excel workbooks hosted in Power BI Report Server losing support. On the proposed timeline, many critical SharePoint/Exchange or air-gapped farms won’t migrate safely; the likely outcome is running OOS unsupported, which increases security risk — the opposite of the stated goal.

    Extend OOS support by 3–5 years (e.g., to 2030/2031) under a security-only LTS track with fixes only.
    Provide a containerized OOS LTS image suitable for disconnected environments with predictable patching.
    Ship an official on-prem “Viewer” (preview and conversion) for SharePoint/Exchange SE to preserve search previews and document viewing.
    For customers who can use cloud, deliver a supported hybrid connector to render via Office for the Web with strong compliance controls (proxy, cache, ADFS/Entra ID, auditing).
    Licensing transparency: if OOS functionality is removed from on-prem offerings, align pricing accordingly (Office LTSC/SharePoint CAL).

    The timeline is too short for critical and constrained workloads; removing OOS now degrades productivity and pushes customers into unsupported operation.
    OOS is not optional: it enables browser previews, editing, and co-authoring on-prem; cloud “alternatives” do not help those who must remain disconnected.
    Specific scenarios break (for example, Excel in Power BI Report Server) with no functional equivalent in isolated environments.

    PS: Modernization is welcome; abandoning on-prem isn’t. A secure LTS track plus a supported hybrid bridge maintains trust, reduces risk, and provides a realistic runway to migrate.

    Even Bill Gates would agree with me.

  • broland's avatar
    broland
    Iron Contributor
    Oct 29, 2025

    While this doesn't really affect me (we have one setup but it is not heavily used) I would think it is going to be a major issue for some and I have to confess I'm kind of tired of the constant rug pulls of good products from Microsoft.    

    • Gandalfse's avatar
      Gandalfse
      Copper Contributor
      Oct 24, 2025

      I am sorry to see yet another attempt to strong arm us in to migrate to the cloud.

      (Comments don´t work in chrome) 

       

  • JereckNET's avatar
    JereckNET
    Brass Contributor
    Oct 21, 2025

    That's it ? No replacement ?

    What about SharePoint on-premises ?