FreeFileSync - FreeFileSync is a free open source data backup software that helps you synchronize files and folders on Windows, Linux and macOS.

Dropbox - Online Sync and File Sharing

rsync - rsync is a file transfer program for Unix systems. rsync uses the "rsync algorithm" which provides a very fast method for bringing remote files into sync.

ownCloud - ownCloud is an open source project enabling businesses to host their own cloud storage while maintaining regulatory and compliance needs.

GoodSync - GoodSync provides highly reliable file backup and synchronization for both individuals and businesses.

Box - Box offers secure content management and collaboration for individuals, teams and businesses, enabling secure file sharing and access to your files online.