Office Web Add-in limits and considerations with respect to files

Question

Hello there. I had some questions regarding office web add-ins:

1. Is it possible to access user's local file systems through these add-ins in any way ?
2. Are there parts of web API closed off ?
3. Is cookie based authentication supported if OAuth isn't implemented at server ?

Answer 1

Hi HariMohan-7655,

1. Our goal with Office Add-ins is to write a model that will work across devices and browsers as such direct access to the file system is not available. Consider using the Microsoft Graph to access the users OneDrive as a cloud-friendly way of potentially achieving similar results.
2. I'm not sure what you mean by Web API in this case. Can you elaborate?
3. A lot of cookie-based authentication works because our platform is based on browser IFrames and native WebView controls. There are some known limitations that affect 3rd party cookies that you may need to be aware of - https://learn.microsoft.com/en-us/office/dev/add-ins/develop/itp-and-third-party-cookies

Answer 2

I would also like to know if on-prem solutions are possible ? In case it isn't, what is the recommended way forward for hosting these add-ons ?

Answer 3

Your Add-in is able to get oauth and other tokens (with or without prompting users for logins), and can then use them for most of the Microsoft API's, which includes saving arbitrary stuff inside user Roaming Profiles, as well as use EWS and Graph - which probably grants you access to OneDrive files that way.