Duplicati

Duplicati is a backup client that writes encrypted, compressed and deduplicated archives to a destination of your choosing: a local disk, a network share, an SFTP or WebDAV server, or one of many cloud object stores. The point is to decouple the backup software from the storage, so a cheap bucket or an existing cloud account can hold versioned backups that the provider cannot read. Every backup job is defined once, then runs on a schedule, and restores are performed from the same interface by picking a point in time.

How a backup job works

You create a job, list the source folders, choose a destination, and set a passphrase that encrypts the archive. The first run uploads a full copy; later runs compare file blocks against the local job database and upload only what changed, which keeps daily transfers small even for large folders. The application keeps a catalogue of versions, so you can restore a single file as it looked on a given date or roll a whole folder back, either to the original location or somewhere else side by side. Options exist for retention rules that thin out old versions automatically, for bandwidth and CPU throttling, and for running a verification pass that re-reads remote data and compares hashes so silent corruption does not go unnoticed.

Choosing the destination and the settings that matter

Destinations include local folders, SMB shares, SFTP and FTP servers, WebDAV, and cloud targets such as S3-compatible storage, Backblaze B2, Microsoft OneDrive and Azure, Google Drive and Cloud Storage, Dropbox, Box, Mega, pCloud, Storj and others, with rclone as a generic bridge. The passphrase is the most important setting: without it the archive cannot be restored, and the developers cannot help. Retention policy is the second: keeping every version forever grows storage without limit. The pause and resume controls, plus the option to run only when a specific network or schedule condition is met, matter more on laptops than on desktops.

Limits worth knowing before you rely on it

Duplicati protects files, not the operating system: it is not an image-based tool, so recovering a dead system still requires reinstalling Windows and then restoring data. Restores depend on the local job database, and if that database is lost it has to be rebuilt by reading the remote archive, which can take a long time on a large backup. Very large first backups take hours, and some cloud providers throttle the many small requests a deduplicating client generates. The command-line tools shipped with the package allow headless scheduling and scripted restores if you prefer not to keep the tray application running.

When a different approach is better

If you need a bootable image of a whole machine, an imaging product is the correct category. If you simply want two folders kept identical, a synchronisation tool is faster and easier to reason about. Duplicati fits people who already have storage somewhere, want versioned and encrypted off-site copies, and are willing to verify a restore once rather than assume the backup works.