How to install Microsoft on Mac with older operating system

Tony 0 Reputation points
2026-11-11T18:11:22.0533333+00:00

Install Microsoft 365 Office build compatible with macOS Catalina 10.15.7, instead of the current installer that requires a newer macOS version.

Microsoft 365 and Office | Install, redeem, activate | For home | MacOS
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  1. Vikki-T 14,115 Reputation points Microsoft External Staff Moderator
    2026-11-12T08:57:38.4+00:00

    Hi Tony,

    I understand that you need an Office version that can be installed on macOS Catalina 10.15.7. Version 16.66 was the last Office for Mac release compatible with Catalina, so the older installer suggested in the AI answer is the appropriate version to look for in Microsoft’s official Office for Mac update history.

    However, there is an important current limitation to consider. Catalina is no longer a supported macOS version, and Microsoft states that Office on older unsupported operating systems may enter reduced functionality mode. In that state, the apps may still open or print documents but may no longer allow you to create, edit, or save them.

    Therefore, installing version 16.66 may help you install Office, but it cannot guarantee continued full Microsoft 365 functionality or security updates. If your Mac cannot be upgraded to at least macOS Monterey, you may need to use Microsoft 365 for the web or a device that supports a newer macOS version.

    Please note that this is a user-to-user support forum. Moderators, contributors including external Microsoft employees cannot directly intervene in Microsoft product features or access back-end systems. My role is limited to providing technical guidance on reported issues, requests, or ideas. Thank you so much for your understanding. 

    Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

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  2. AI answer

    2026-11-11T18:12:10.9366667+00:00

    Install Microsoft 365 for Mac version 16.66/16.66.1, rather than the current installer, because this older build is compatible with macOS Catalina 10.15.7.

    Install the Catalina-compatible build

    1. Close all Microsoft Office applications.
    2. If the incompatible current release is partly installed:
      • Open Finder → Applications.
      • Control-click each Office application and select Move to Trash.
    3. Download the Microsoft-hosted Office 16.66.1 full installer: Microsoft Office 16.66.1 installer This installer was the accepted resolution for the same Catalina 10.15.7 installation problem.^1^
    4. Open Finder → Downloads, double-click the downloaded .pkg, and complete the installation.
    5. Open Word or Excel and sign in with the Microsoft account associated with the active Microsoft 365 subscription. A valid licensed account is required to create and edit files.^2^
    6. Confirm the installed version from Word → About Microsoft Word. It should show version 16.66.x.

    Microsoft’s official release history lists the October 2022 Office 16.66 full installer and the 16.66.1 application updates.^3^

    Important limitation

    Catalina is outside the currently supported macOS range. Office can continue to work on an unsupported macOS version, but it no longer receives feature or security updates.^4^

    If the Mac can be upgraded, that is the safer long-term option. If it cannot, use the older desktop build with that limitation in mind, or use Microsoft 365 on the web for a currently maintained experience.^5^

    If installation or activation fails

    • If the .pkg does not open, wait until the download finishes, move it from Downloads to the desktop, and open it there.
    • If Office installs but shows the wrong license, remove the existing Office license files and reactivate using the account tied to the Microsoft 365 subscription.^2^
    • If Microsoft AutoUpdate offers a release requiring a newer macOS version, do not install that release while remaining on Catalina.

    References

    1. how to install 365 on my Mac OS catalina 10.15.7 - Microsoft Q&A
    2. [Activation](https://support.microsoft.com/microsoft-365-activation-licensing/what-to-try-if-you-can-t-install-or-activate-office-for-mac)
    3. Update history for Office for Mac
    4. Upgrade macOS to continue receiving Microsoft 365 and Office for Mac updates | Microsoft Support
    5. Update Microsoft 365 or Office on your macOS or iOS device | Microsoft Support
    AI-generated content may be incorrect. Read our transparency notes for more information.

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    2 people found this answer helpful.

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