The default language in SharePoint and OneDrive have impact on eg. spell-check in Office online apps. To check the default language in SharePoint online install the PowerShell module for SPO (https://www.microsoft.com/en-us/download/details.aspx?id=35588). Connect to the SPO-service: Connect-SPOService -Url https://TENENT-admin.sharepoint.com Ones connected run: Get-SPOSite -Detailed -Limit All | select Url,LocaleId You can…