Unison File Synchronizer icon
Unison File Synchronizer icon

Unison File Synchronizer

 95 likes

Unison is a file-synchronization tool for POSIX-compliant systems (e.g. *BSD and GNU/Linux), macOS and Windows, with the caveat that the platform must be supported by OCaml. It allows two replicas of a collection of files and directories to be stored on different hosts (or diffe.

Unison running in KDE terminal window

License model

  • FreeOpen Source

Application type

Country of Origin

  • US flagUnited States

Platforms

  • Mac
  • Windows
  • Linux
  • Flathub
  • Flatpak
  • Snapcraft
4.3 / 5 Avg rating (6)
95likes
7comments
0news articles

Features

Suggest and vote on features

Properties

  1.  Privacy focused
  2.  Lightweight

Features

  1.  Bidirectional sync
  2.  Synchronization
  3.  File Sync
  4.  2 way sync
  5.  Folder Sync
  6.  Command line interface
  7.  Gtk
  8.  Decentralized
  9.  Support for Rsync
  10.  No registration required
  11.  Works Offline
  12.  No Tracking
  13.  Selective Synchronization
  14.  Ad-free
  15.  Dark Mode
  16.  File Versioning
  17.  Well documented

 Tags

  • command-line-start
  • database-replication

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Unison File Synchronizer information

  • Developed by

    US flagBenjamin C. Pierce
  • Licensing

    Open Source (GPL-3.0) and Free product.
  • Rating

    Average rating of 4.3
  • Alternatives

    53 alternatives listed
  • Supported Languages

    • English

AlternativeTo Categories

Backup & SyncOS & Utilities

GitHub repository

  •  4,629 Stars
  •  247 Forks
  •  105 Open Issues
  •   Updated May 25, 2025 
View on GitHub

Our users have written 7 comments and reviews about Unison File Synchronizer, and it has gotten 95 likes

Unison File Synchronizer was added to AlternativeTo by Mutant on Jul 2, 2009 and this page was last updated May 12, 2025. Unison File Synchronizer is sometimes referred to as Unison.

Comments and Reviews

   
 Post comment/review
Top Positive Comment
Guest
Apr 29, 2020
1

An effective tool. does what is built for. I use it since about 10 years, flawlessy, in a home environment with 3-4 devices.

Top Negative Comment
Shuunen
Jul 25, 2020
0

Not easy to use IMHO

axcqhsbsadoukciozt
Jul 18, 2022
0

Stop looking, this is the best synchronization tool hands down when you have a workstation and a laptop and may files. They thought of all possible details and edge cases. You can unplug the network cable while synchronizing and noting bad will happen. In case of conflict you always decide what to do. The protocol, when tunneled over SSH saturates my 1GBPS network card, and is performant even when many small files are synchronized. The GUI may look outdated but it works flawlessly; it's rock solid and very reliable.

QueenD
Oct 5, 2020
-1

No way the best for me are CopyWhiz and Gs Richcopy 360, but I will give Unison a try!

Shuunen
Jul 25, 2020
0

The GTK sdk will be needed, I used https://sourceforge.net/projects/gtk-win/

creeperlava
Jan 22, 2018
1

Best synchronization software with GUI there is.

ShieldEdge
Nov 2, 2017
0

Cross-platform, highly customizable, well documented, can be made into a service with NSSM

What is Unison File Synchronizer?

Unison is a file-synchronization tool for POSIX-compliant systems (e.g. *BSD and GNU/Linux), macOS and Windows, with the caveat that the platform must be supported by OCaml. It allows two replicas of a collection of files and directories to be stored on different hosts (or different disks on the same host), modified separately, and then brought up to date by propagating the changes in each replica to the other.

Unison has been in use for over 20 years and many people use it to synchronize data they care about.

Unison shares a number of features with tools such as configuration management packages (CVS, Subversion, git, Mercurial, etc.), distributed filesystems (Coda, etc.), uni-directional mirroring utilities (rsync, etc.), and other synchronizers. However, there are several points where it differs:

  • Unison runs on almost any system with an OCaml compiler. Moreover, Unison works across platforms, allowing you to synchronize a Windows laptop with a Unix server, for example.

  • Unlike simple mirroring or backup utilities, Unison can deal with updates to both replicas of a distributed directory structure. Updates that do not conflict are propagated automatically. Conflicting updates are detected and displayed.

  • Unlike many network filesystems, Unison copies data so that already-synchronized data can be read and written while offline.

  • Unlike most distributed filesystems, Unison is a user-level program that simply uses normal systems calls: there is no need to modify the kernel, to have superuser privileges on either host, or to have a FUSE implementation.

  • Unison works between any pair of machines connected to the internet, typically communicating over ssh, but also directly over TCP. It is careful with network bandwidth, and runs well over slow links such as PPP connections. Transfers of small updates to large files are optimized using a compression protocol similar to rsync.

  • Unison is resilient to failure. It is careful to leave the replicas and its own private structures in a sensible state at all times, even in case of abnormal termination or communication failures.

  • Unison has a clear and precise specification.

  • Unison is Free; full source code is available under the GNU Public License, Version 3.