We have a customer trying to access content of excel document that is in SharePoint online document library through API.
Can anyone point out to proper documentation on how this can be done or any suggestions will be helpful
Thanks in advance.
You'll have to use the Excel API, which is available in SharePoint Online. Here are articles that explains how it works and the first steps:
https://blogs.office.com/2013/12/17/excel-rest-api-in-sharepoint-online/ https://dev.office.com/sharepoint/docs/general-development/excel-services-rest-api