OfficeRuntime.Storage: Where is the data actually stored on Excel Desktop & Web?

ltrcx 1 Reputation point

Hello, I have an excel add-in that has some custom functions (functions.html, functions.js...) and a task pane. It's not using the shared runtime. Task pane has some html inputs to get credentials from the user. These credentials are stored with Then these are accessed within the custom functions to make an API call.

The data is shared with the between task pane and the custom functions.

I read the documentation but there is not much detail about where the data is stored. I've investigated the web version and I see that the data created with is actually stored in local storage. I wonder where exactly the data is stored on Excel Desktop.

Is it saved in user's computer where the Excel is running? Is is possible to access these credentials from another add-in running on the same computer? I want to make sure that the data I stored with is isolated from other users and other add-ins.

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An Office service that supports add-ins to interact with objects in Office client applications.
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Office: A suite of Microsoft productivity software that supports common business tasks, including word processing, email, presentations, and data management and analysis.Development: The process of researching, productizing, and refining new or existing technologies.
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  1. ltrcx 1 Reputation point

    Official answer:

    Yes. For add-in on Excel online, the data created with is stored in local storage.
    For add-in on Excel Desktop, each add-in has an independent sandbox that guaranteed the runtime(and the data) of one add-in is isolated from other add-ins. The data stored with is stored in the corresponding local storage.

    Here is another documentation about for reference.

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