Problem: SharePoint doesn’t allow you to delete a site with its sub-sites. In other words, You cannot delete a SharePoint Subsite that has one or more child subsites. You’ll have to individually remove each and every child subsite prior to removing the parent subsite.
Can’t delete subsite in SharePoint 2013:
You’ll end up in these errors if you try to delete a site with its subsites.
Sorry, something went wrong
There was a problem deleting Web site “/Subsite”. Sites that have subsites or certain apps can’t be deleted. Please try again after deleting all subsites and removing the apps.
SharePoint 2007 Error: Error deleting web site “/subsiteurl”. You can’t delete a site that has subsites.
So, to delete a site with subsites in SharePoint, first, we have to delete all child subsites and then delete the parent site. What if you
have a large number of subsites?
Solution: Use “Content and Structure Manager”.
Here is the quick trick to delete a subsite from the SharePoint site:
Go To: Site Actions >> Site Settings >> Under Site Administration, click on the “Content and Structure” link. (In SharePoint 2013, its “Content and Structure Logs”)Select the check-box on each subsite you want to delete, and choose the “Delete” button from the “Actions” menu.
Please note, Content and structure feature is based on “Publishing Feature”. You must enable Publishing feature to get content and structure. Obviously, Its not available in SharePoint Foundation!
To delete a site with subsites in SharePoint Online, use: SharePoint Online: delete site with subsites