In May 2022, Apple will stop syncing old documents and data to iCloud to keep iCloud Drive only. This development Advertise Its support page also explains how to activate iCloud Drive.
Affected users are those who have Mac and iOS devices running at least with OS X Yosemite (10.10) for some and iOS 8 for others (plus Windows 7 for PCs).
ICloud Drive was announced 7 years ago, during WWDC 2014. You may have already activated it since or during your device renewal or system updates.
The service received a huge improvement after two years with full synchronization between platforms. ICloud Drive lets you keep synchronous Between Mac, PC, iPhone, iPad, web files stored in Documents folder, those left on Desktop, and shared folders since last year.
If this migration to iCloud Drive was not done manually as of May 2022, it will be performed automatically. For devices still running prior to iOS 8 and Yosemite, the cloud sync feature will be discontinued within one year.