With the Office Add-ins platform, you can extend Excel’s functionality
through a web app that runs within the Excel client on multiple platforms such as Windows,
Office.js. To learn more about creating an Excel add-in with Office.js, see Excel add-ins documentation.
With Microsoft Graph, you can read and modify Excel workbooks that are
stored in OneDrive, SharePoint, or other supported storage platforms. By issuing REST API
requests to Microsoft Graph, your web or mobile application can access Excel objects. To learn
more, see Working with Excel in Microsoft Graph.