rsync!

Syncthing replaces proprietary sync and cloud services with something open, trustworthy and decentralized. Your data is your data alone and you deserve to choose where it is stored, if it is shared with some third party and how it's transmitted over the Internet.

FreeFileSync is a free Open Source software to synchronize files and synchronize folders available for Windows, Linux and Mac OS X. It is designed to be easy to use while having nice visual feedback along the way.

GoodSync is the high-end professional easy and reliable file backup and file synchronization software.

SyncBack is a backup and file synchronization software that allows backing up and synchronizing files to the same or different drives, to different media (CD, DVD, Flash, zip), or to a remote server.There are three versions of SyncBack available: SyncBack Freeware, SyncBackSE (shareware) or SyncBackPro (shareware).

Rclone is a command line program to sync files and directories to and from:- Google Drive- Amazon S3- Openstack Swift / Rackspace cloud files / Memset Memstore- Dropbox- Google Cloud Storage- Amazon Cloud Drive- Microsoft One Drive- Hubic- Backblaze B2- Yandex Disk- The local filesystem

Déjà Dup is a simple backup tool. It hides the complexity of doing backups the 'right way' (encrypted, off-site, and regularly) and uses Duplicity as the backend. It features support for local or remote backup locations, including Amazon S3.

Simple fast backup for Windows. At a glance - small and very lean, very fast delta copier, excellent user interface, device tracking, shadow copying, move/rename detection, run-as-a-service mode, robust support for multi-million item backups with terabytes of data, intelligent and discrete update mechanism. Ideal for backups going to external USB drives and NAS devices.

SyncToy is a free PowerToy designed by Microsoft, that provides an easy to use graphical user interface that can automatically synchronize local or network files and folders, but not WebDAV-, "Windows Mobile" files or folders and no triangle-sync as only Allway Sync, Synkron, SyncLess or GoodSync can do. No VSS-support, not portable. SyncToy can manage multiple sets of folders at the same time; it can combine files from two folders in one case, and mimic renames and deletes in another case. Unlike other applications, SyncToy actually keeps track of renames to files and will make sure those changes get carried over to the synchronized folder. »

Grsync is a rsync gui, a graphical user interface for the rsync file synchronization and backup tool. It works on linux, solaris, windows, mac os x and maemo. It uses the gtk libraries and can work under the gnome desktop.

Create Synchronicity is a nice, lightweight backup program with a very user-friendly - yet powerful - interface, that synchronizes files and folders extremely quickly (it can even recognize paths such as "MyUSB"\MyFolder, and locate the USB drive called "MyUSB").Its open source, fully portable, and multilingual ; and it can schedule backups and has many advanced options like DST correction and regexp settings.

Back In Time is a simple backup tool for Linux inspired from FlyBack and "TimeVault". The backup is done by taking snapshots of a specified set of directories.

DirSync Pro (Directory Synchronize Pro) is a small utility for file and folder synchronization without bidirectional file-deletion. DirSync Pro can be used to synchronize the content of one or many folders recursively. In difference to Allway Sync, SyncBack or Synkron in the bidirectional synchronizing mode no files can be deleted!Using DirSync Pro you can make incremental backups. Only new/modified/larger files would be copied.Use DirSync Pro to easily synchronize files from your desktop PC to your USB-stick.DirSync Pro is programmed completely in platform independent Java. »