Duplicacy vs Kopia: Which Backup Tool to Self-Host?

Duplicacy is one of the few backup tools that supports lock-free, cross-machine deduplication — meaning multiple computers can back up to the same storage without coordinating with each other. Kopia takes a different approach with snapshot-based deduplication and ships a built-in web UI that Duplicacy charges extra for.

Quick Verdict

Kopia is the better choice for most self-hosters. It’s fully open-source (Apache 2.0), includes a web UI at no cost, has an active community with 12,700+ GitHub stars, and covers every common backup scenario. Duplicacy’s lock-free cross-machine dedup is technically impressive, but the commercial GUI licensing and smaller community make it harder to recommend for typical home server use.

Overview

Duplicacy is a cloud backup tool built on a patented lock-free deduplication algorithm (published in IEEE Transactions on Cloud Computing). Its CLI is free for personal use; the web GUI requires a $50/year commercial license. The unique selling point is that multiple machines can back up to the same storage simultaneously without a central coordinator — each machine deduplicates independently against the shared chunk pool. Version 3.2.5 is the current stable release.

Kopia is a fully open-source backup tool (Apache 2.0) that uses snapshot-based deduplication with client-side encryption, compression, and error correction. It includes a built-in web UI (KopiaUI) and CLI with full feature parity. With 12,700+ GitHub stars and 150+ contributors, it’s one of the fastest-growing backup tools in the self-hosted ecosystem. The latest stable release is v0.22.3 (December 2025).

Feature Comparison

Feature	Duplicacy	Kopia
Deduplication	Lock-free, variable-size chunking	Snapshot-based with content-defined chunking
Cross-machine dedup	Yes (no coordinator needed)	Yes (via shared repository)
Encryption	AES-256-GCM	AES-256-GCM, ChaCha20-Poly1305
Compression	zstd, lz4	zstd, s2, pgzip, gzip
Web UI	Separate commercial product ($50/year)	Built-in (free, same binary)
CLI	Free (personal use)	Free (Apache 2.0)
Docker image	Community only (erichough/duplicacy)	Official (kopia/kopia)
Cloud backends	17+ (S3, Azure, GCS, B2, Dropbox, OneDrive, Wasabi, WebDAV, SFTP)	8+ native (S3, Azure, GCS, B2, WebDAV, SFTP) + Rclone
FUSE mount	No	Yes (browse snapshots as filesystem)
Policy engine	Retention by count/age	Full policy system (retention, compression, scheduling)
Server mode	No (CLI + web GUI)	Yes (Kopia Repository Server for centralized management)
Error correction	No	Built-in (Reed-Solomon)
License	Free CLI (personal) / $50/yr commercial	Apache 2.0 (fully open-source)
GitHub stars	~2,100	~12,700

Installation Complexity

Kopia has an official Docker image and a straightforward setup. Run the server, connect to a repository (local or cloud), and start defining backup policies through the web UI.

# Kopia — repository server mode
services:
  kopia:
    image: kopia/kopia:0.22.3
    ports:
      - "51515:51515"
    command: server start --address=0.0.0.0:51515 --insecure
    volumes:
      - kopia-config:/app/config
      - kopia-cache:/app/cache
      - kopia-repo:/repository
      - /data/to/backup:/source:ro
    restart: unless-stopped

Duplicacy has no official Docker image. Community-maintained images exist (erichough/duplicacy), but setup requires more manual steps — initializing a storage backend from CLI, configuring backup schedules, and (if you want the web GUI) licensing separately.

Setup Step	Duplicacy	Kopia
Docker image	Community (unofficial)	Official
Initial repository setup	CLI: duplicacy init	CLI or web UI
Web UI	Separate install + $50/yr license	Built-in (zero cost)
Cloud backend config	CLI flags	CLI, web UI, or config file
Scheduling	External (cron) or web GUI	Built-in policy engine
Time to first backup	15–30 min	5–10 min

Performance and Resource Usage

Both tools are written in Go and have similar raw backup performance. Duplicacy’s lock-free architecture gives it an edge in multi-machine scenarios — no contention or locking when several machines back up simultaneously.

Kopia’s snapshot-based approach includes built-in error correction (Reed-Solomon codes), which adds marginal overhead but protects against bit rot in the repository.

Resource	Duplicacy	Kopia
RAM (backup operation)	100–300 MB	150–400 MB
CPU	Moderate (chunking + encryption)	Moderate (chunking + encryption + error correction)
Disk (application)	~30 MB (CLI)	~50 MB
Dedup ratio (typical)	High (variable-size chunks)	High (content-defined chunks)
Concurrent backup support	Lock-free (multiple machines, no contention)	Locking per snapshot (safe but sequential per source)

Community and Support

Kopia has strong community momentum: 12,700+ GitHub stars, 150+ contributors, active Slack and Discourse forums, and regular releases through 2025–2026. Documentation covers Docker, CLI, server mode, and every backend configuration.

Duplicacy has a dedicated community (~2,100 GitHub stars) centered around its forum. Development is steady but slower-paced. The academic backing (IEEE publication) gives the project technical credibility. Support for the web GUI goes through the commercial license.

Use Cases

Choose Duplicacy If…

• You back up multiple machines to the same cloud storage and want lock-free deduplication
• You need cross-computer dedup without a central server (each machine operates independently)
• You’re managing backup costs across 17+ cloud providers and want to pick the cheapest option
• You’re comfortable with CLI-first workflow and don’t need a web UI (or will pay for one)

Choose Kopia If…

• You want a fully open-source backup solution with no paid tiers
• You need a built-in web UI for managing backup policies and browsing snapshots
• You want FUSE mount support to browse backed-up files as a regular filesystem
• You prefer official Docker images and straightforward container deployment
• You want built-in error correction to protect against storage bit rot

Final Verdict

Kopia is the better choice for most self-hosters. The combination of a fully open-source license, built-in web UI, official Docker image, FUSE snapshot browsing, and error correction makes it the more complete package. Setup is faster, the community is larger, and you never hit a paywall for any feature.

Duplicacy’s lock-free cross-machine deduplication remains technically unique — if you’re backing up 5+ machines to the same B2 bucket and want zero coordination overhead, Duplicacy’s architecture is purpose-built for that scenario. But for typical home server backups (1–3 machines, one storage target), Kopia does everything you need without the licensing complexity.

Frequently Asked Questions

Can Duplicacy and Kopia share the same storage backend?

No. Each tool uses its own repository format. You’d need separate storage paths or buckets for each.

Does Kopia support Dropbox and OneDrive?

Not natively, but Kopia can use Rclone as a backend, which supports both Dropbox and OneDrive (marked experimental). Duplicacy has native support for both.

Is Duplicacy’s CLI really free?

Yes — the CLI is free for personal use. Commercial use requires a license. The web-based GUI is a separate product that requires a $50/year per-computer license regardless of use case.

Related

• Self-Hosting Duplicacy for Cloud Backup
• How to Self-Host Kopia
• How to Self-Host Duplicati
• Duplicacy vs Restic
• Best Self-Hosted Backup Solutions
• Backup Strategy: The 3-2-1 Rule
• Docker Compose Basics