Duplicacy

Duplicacy is a cross-platform backup tool designed for fast, encrypted, deduplicated backups to local, SFTP, and many cloud storage providers. It uses a lock-free deduplication design that allows multiple clients to back up to the same repository without requiring distributed locks or a centralized chunk database.

Key Features

• Lock-free, cross-client deduplication enabling concurrent backups to the same storage target
• Database-less chunk storage (chunks stored independently by hash) for simple lookups and reduced metadata complexity
• Encrypted backups with support for stronger asymmetric encryption options
• Full-snapshot incremental backups, with support for deleting/pruning old backups
• Data integrity checking and repository maintenance workflows (e.g., check and prune)
• Broad storage backend support including local disk, SFTP, S3-compatible/object storage, and various cloud drives
• Command-line interface plus an optional web-based GUI application built on the same backup engine

Use Cases

• Centralized backups for multiple machines to a shared NAS/SFTP or cloud bucket with cross-machine deduplication
• Efficient long-term backup retention with pruning of old snapshots
• Offsite backups to common cloud/object storage providers while keeping data encrypted

Limitations and Considerations

• The command-line version is source-available but not OSI open-source; commercial use typically requires per-computer licensing for running backups

Duplicacy focuses on reliability, performance, and storage efficiency, particularly for multi-client repositories. It is well-suited for individuals and teams that want deduplicated, encrypted backups to commodity storage backends without lock coordination overhead.