Syncthing vs duplicity

Licensed under MIT.

Available for Linux, OS X and Windows and web.

Requires no configuration to protect your privacy; it just works.

An Android app was created by a third-party.

Data is encrypted locally before being sent, and kept encrypted by a key that is never stored on the remote machine. So you might even store your data on a public space, people would still need your key or brute force it.

Duplicity uses the rsync algorithm so only the changed parts of files are sent to the archive when doing an incremental backup. For instance, if a long log file increases by just a few lines of text, a small diff will be sent to and saved in the archive. Other backup programs may save a complete copy of the file.

You can retrieve older versions or files you recently deleted locally even after having updated your backup.

Licensed under GNU GPL v2.

Duplicity does not make many demands on its archive server. As long as files can be saved to, read from, listed, and deleted from a location, that location can be used as a duplicity backend. Besides increasing choice for the user, it can make a server more secure, as clients only require minimal access.

Docker allows to run programs on any Linux without having to really install them, and allows to manage versions so it runs exactly the same on different machines.