September 2021 CU for Office Online Server is available for download

The product group released the September 2021 Cumulative Update for Office Online Server.

The KB article for September 2021 CU will be available at the following Location in a couple of hours:

  • KB 5001999 – September 2021 Update for Office Online Server

The download for September 2021 CU is available through the following link:

Related Links:


  1. Stefan, you must get this question often. I ask because I hear conflicting advice. Is the procedure “Apply software updates to Office Online Server” required for CUs like this, or does it only apply to major changes like service packs? Thank you.


    1. Hi Pete,
      the information I have received from my colleagues who are supporting Office Online Server is that this article applies to all types of updates.


      1. Thanks Stefan, appreciated


  2. Hey Stefan. I have one question. We are using an Office Online Server from Office Professional Plus 2016. Does this update also applies to this 2016 version, or is it only for the 2019 version? I can’t find any updates for the 2016 version younger than KB3213659 from 2017-07-10. Is this correct?
    Thanks and kind regards


      1. Hey Stefan,
        wow, thanks for your fast reply. We have exactly that version installed (16.0.10338.20039). But where do I get the updates from? And where can I check what the latest update is?


        1. If you scroll up to the top of this article you will find the download link for the latest update.


          1. Yeah. Thanks. 😉 I know. So this answers my first question, that I can use this update for our 2016 version as well. Thanks for that.

          2. This seems to be a common confusion. There is only exactly ONE version of Office Online Server.
            No 2016 version and no 2019 version. Office Online Server is evergreen.

          3. Ahh, now I see the light. That was the missing information. Thanks for that!

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