Duplicati

Duplicati is a free, open-source backup client that encrypts your data before sending it anywhere. You configure a backup job, point it at a source, pick a destination from a long list of supported storage providers, and Duplicati handles the rest: deduplication, compression, AES-256 client-side encryption, and configurable retention schedules.

The storage backend list covers essentially everything: AWS S3, Backblaze B2, Google Drive, OneDrive, Azure Blob, SFTP servers, WebDAV, and more than 30 others. Because encryption happens client-side before data leaves your machine, you can use cheap untrusted cloud storage without giving the provider access to your files.

A web-based UI runs on the same machine as the backup agent, making setup accessible without command-line knowledge. Scheduling is flexible, incremental backups keep bandwidth usage low after the initial run, and you can restore individual files without downloading the full backup set.

The free tier allows monitoring of up to two machines through the optional cloud console. Paid plans extend this to larger fleets, though the backup agent itself is always free to use.

Duplicati has been around since 2008 and has a strong reputation in the self-host community. A known caveat is that some users have historically encountered database corruption issues on very large backup sets after long uptimes. Running regular restore tests is advisable with any backup software, and Duplicati is no exception.