Kopia

Kopia is an open-source backup tool that takes a different approach to backup software than most: it is fast, storage-efficient, and has both a polished desktop UI and a full CLI, so it works equally well for technical and non-technical users.

Every backup is stored as an encrypted, deduplicated, compressed snapshot. Deduplication happens at the block level across snapshots, so storing a year of daily backups for a directory that barely changes takes a fraction of the space you would expect. Encryption is end-to-end and user-controlled: Kopia never handles your keys.

Storage backend support covers all the major cloud providers and local options: Amazon S3, Azure Blob, Google Cloud Storage, Backblaze B2, WebDAV, SFTP, and any Rclone-supported provider (which adds Dropbox, OneDrive, and Google Drive). You can store snapshots on multiple backends simultaneously for redundancy.

The desktop application (KopiaUI) covers policy management, scheduling, and manual snapshot browsing with a visual interface. The CLI offers the same functionality for scripting and automation. A Kopia Repository Server mode lets you centralize snapshot management across multiple machines.

With 13,000+ GitHub stars and Apache 2.0 licensing, Kopia has built a strong reputation as a fast and reliable backup tool. The main trade-off is that there is no centralized backup console for monitoring fleets of machines the way some commercial tools provide; each machine manages its own policy.