The SharePoint Lists and Libraries experience setting

Microsoft is starting to modernize the SharePoint platform by adding new modern experiences for pages as well as lists and libraries. If your users already have experience with SharePoint either online or on-premises, you may want to have the lists and libraries use the classic experience:

If your users are new to SharePoint, then you may want to use the modern experience:

Another option is to set the experience to modern in the SharePoint admin center, then change the experience on a case ...

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