Syncthing allows you securely to backup data without the need to trust a third-party cloud provider. Data is backed up to a computer or server that you directly control, and is at no point stored by a third party. The encryption used is also fully end-to-end, as you encrypt it on your device, and only you can decrypt it. No-one else holds the encryption keys.

It supports file versioning. If this option is used, Syncthing will archive older versions of files when they are saved over or deleted. They can that can be accessed at a later point. This is configured on a per-folder basis, and you decide how many previous versions of a file will be archived.

Once setup, Syncthing is a fantastic way to securely backup files between your all your computers and mobile devices. It is also a great way to simply transfer files between them wirelessly. This is done in a simple and intuitive way (just drop your files in the sync folder, and they will magically appear in the matching folder on the other device).