Bittorrent Sync review: synchronize files locally or on the Internet

Martin Brinkmann
Feb 1, 2013
Updated • Feb 3, 2013

Bittorrent Sync is a new file synchronization software for local area networks and remote servers based on the popular Bittorrent protocol that was announced a week ago. The program is not publicly available yet and interested users can sign up to participate in an alpha test.

Program downloads are provided for Microsoft Windows, Apple Mac OS X and Linux systems. You need to install the program on at least two computer systems that are connected to the same local area network. Once you have installed the program on the first system run it and add at least one folder to it that you want to keep in sync between your systems.

You generate a random key during the process that you need to pair computer systems in the network. Note that you generate keys for each folder that you want to share. The key basically connects devices into a sync network.

Once you have added one or multiple shared folders on the first system, run the Sync client on another computer system and use the previously generated key for the pairing of devices. The other system is automatically picked up and the synchronization starts right away afterwards.

The devices in sync are connected directly. Сonnection is established by use of UDP, NAT traversal, UPnP port mapping, and relay server. If your devices are in a local network, SyncApp will connect them in LAN and synchronize them without the Internet.

You can check current transfers and the transfer history in the interface, and also the devices that files are synced to. The preferences let you change the network listening port, disable NAT UPnP port mapping, limit the download or upload rate and change the name of the device that is displayed on other systems.

It should be clear that both computer systems need to be connected to the local area network or online for the synchronization to work, as no master server or cloud storage is used to cache files if that is not the case.

syncapp screenshot

Synchronization here means two-way syncing. If a file exists in the folder on system A but not on B it is transferred, and if a file exists on system B but not on A it is transferred as well. Basically, you end up with identical folder copies on both devices.

System Requirements

  • OSX Snow Leopard or newer
  • Windows XP SP3 or newer
  • Linux with kernel 2.6.15 or newer on ARM/PPC/i386

You can install SyncApp on all Network Attached Storages on Linux with ARM, PowerPC and i386 architecture. SSH access to NAS is required. SyncApp was successfully tested on devices from the following producers: Synology, Western Digital, Iomega.


According to Bittorrent, all traffic between devices is encrypted with AES 256 using a private key that is different for each folder that you synchronize.


  • What happens if files get deleted on one device? Files that are deleted on one device will also be deleted on the other.
  • What happens when a folder is removed? If a folder is removed, all synced files stay on there. Incomplete files however will be deleted.
  • Does SyncApp support versioning? No it does not
  • Does SyncApp support one-way syncing? No it does not

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  1. matti said on June 2, 2013 at 6:20 pm

    Do I understand correctly that Bit Torrent Sync works across LAN only? How does it perform across a VLAN like Hamachi or it’s peers? Have you tried it across IPv6 only?

    1. Martin Brinkmann said on June 3, 2013 at 1:56 am

      Yes it synchronizes over LAN. Have not tried Hamachi or IPv6, sorry.

      1. Remi said on September 18, 2013 at 11:33 pm

        You are so wrong there. I use this daily and have been using it for long time. This is NOT only for LAN. If it was for LAN only why bother? This is kinda like dropbox just without upload any to them servers. Mean you can have machines spread all over the world (Not only LAN) and get them all to synch together which is the beauty of it!

        It’s P2P and why it rocks

  2. Teiji said on February 2, 2013 at 8:08 pm

    If a file is deleted through SyncApp, is it deleted to the Recycle Bin or permanently?

    1. Martin Brinkmann said on February 2, 2013 at 9:13 pm

      It appears to be deleted permanently.

  3. Shadess said on February 2, 2013 at 12:13 am

    No versioning, no way to share a folder without syncing it fully and then just stream it from the other device. Yeah I guess they might add some features but for now it seems this is very much just an automated bittorrent in a sense. If this doesn’t become very succesfull I wonder if they will add any new features that aren’t already in their clients/protocol. For now, I see no reason to move away from AeroFS.

    1. Pongidae said on February 2, 2013 at 4:47 am

      I’ve been waiting for my invite to the AeroFS beta.
      How is it working for ya?

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