BitTorrent Sync is free software, available for all major platforms, that keeps folders in sync across your devices and enables you to share them securely with other people. That may sound suspiciously like Dropbox, iCloud Drive, and dozens of other cloud storage servicesand indeed, the end result is much the same. The big difference is that BitTorrent Sync uses peer-to-peer networking rather than relying on cloud servers.
This approach has several significant advantages. You can have as much storage as you like (limited only by your local disk space) without paying a penny, and because your files are never stored in the cloud, no one else can access them without your explicit permission.
There are downsides too, though. At least one of the computers where your files are synced must be turned on and accessible to the Internet for you to access your files, and youll be subject to your ISPs bandwidth and data caps. Although BitTorrent Sync encrypts your data as it travels between your devices over the Internet, it doesnt encrypt files on diskif you want to do that, youre on your own. And youre unlikely to find many third-party iOS apps with built-in support for BitTorrent Sync, whereas support for Dropbox, iCloud Drive, and other cloud services is common.
For now, I suggest thinking of BitTorrent Sync as a supplement to cloud storage, not a replacement. Even though it has been available for nearly two years and is now at version 1.4, its still considered beta. Although I havent encountered any serious bugs, but some aspects of its user interface are still obscure or confusing, and setup requires a somewhat odd series of steps. Ill walk you through some of the basics.
Once youve downloaded and installed the software, BitTorrent Sync offers several ways to set up syncing between folders on your devices. Ill describe the simplest approach here; for other options, see the online help.
On a Mac that has a folder you want to sync, open the BitTorrent Sync app. Click Add Folder, navigate to the folder you want to sync, select it, and click Open. In the dialog that appears, select Read & Write under Permission (to let yourself modify the folder on any of your own devices). Click Email to create a new message in your default email client, address it to yourself, and click Send.
You can choose Read Only or Read & Write, among other options, when syncing a foldereither with your own devices or with other people.
So far, youve merely made a folder available for syncing. The next step is to set up a peeranother device that will sync this folder.
To set up another Mac as a peer, open the email message you just sent yourself on that Mac and click the link. A webpage opens with two buttons. If the Mac already has BitTorrent Sync installed, click I already have Sync 1.4. If not, click Install Sync 1.4 Beta to download and install the software, and then return to the page and click the other button. (As time goes on, the version number on the buttons will presumably change.)
In the dialog that appears, make sure the path shows the correct location of the folder you want to sync with, which must have the same name (not necessarily the same location) as the one on the first Mac. If not, you can edit it or click Change and navigate to a new location. Be careful hereif youre syncing a folder named Example and you choose, say, /Users/you/Example in this dialog, BitTorrent Sync will add a folder at /Users/you/Example/Example. If you want to sync with an existing folder called Example, choose its parent folder (as in /Users/you) or edit the path manually to eliminate the duplicated folder name. (If the folder you select doesnt already exist, BitTorrent Sync creates it. If it does exist and you click OK at the Add anyway? prompt, the software merges the contents of the folder on the second Mac with the contents of the folder on the first one.) Click Connect.
Read more here:
How to create a personal cloud with BitTorrent Sync