BitTorrent Sync, Dropbox, SKYSITE, Nextcloud, OneDrive, Google Drive and iCloud are prominent products.
[1] However this suffers from the limit that the synchronized files must physically fit in the portable storage device.
Synchronization software that only keeps a list of files and the changed files eliminates this problem (e.g. the "snapshot" feature in Beyond Compare or the "package" feature in Synchronize It!).
The Unison Manual[2] describes how to do this: Common features of file synchronization systems include:[citation needed] Consumer-grade file synchronization solutions are popular, however for business use, they create a concern of allowing corporate information to sprawl to unmanaged devices and cloud services which are uncontrolled by the organization.
[citation needed] When using cloud services, data privacy risks can be mitigated by using a file synchronization solution that features end-to-end encryption instead of simple transport (HTTPS) or at-rest encryption.