To share a folder, select it in BTSync, and then click the Info button in the main menu.
From here it should be pretty obvious what you have to do. The permanent "Read only secret" lets you share the folder with others. Any changes you make will be pushed out to the read-only copy, but any changes made by the recipient of the read-only secret does not sync back to your folder. If you share a text document and give someone full access, then any changes they make to the text document are sent to your devices.
But back to sharing folders! The One-time secret option creates a code that lets you share the folder with others, with either full or read-only access, but the code becomes invalid 24 hours after creation. It's sharing with security in mind. You can also give mobile devices a one-time secret by clicking the Connect mobile device button at the bottom of the Folder Info window.
Advanced features: Versioning and ignoring files
BitTorrent Sync also packs some handy extras that give you additional control over the way your files are stored.
Most helpful is BTSync's version history feature, which let you retrieve older versions of a file you've changed. But BTSync's versioning support isn't obvious by default, and you need to change some Windows settings to view it.
To see your version histories on a synced folder, double-click it in the BTSync interface. This will open the folder in Windows File Explorer. For Windows 8, open the View tab and select the Hidden items check box in the Show/hide section of the menu. (Check out PCWorld's How to View Hidden Files and File Extensions in Windows if you're using Windows 7 or Vista.)
A folder titled ".SyncArchive" will appear in the synced folder. Inside, you'll see a collection of saved, older versions of files you've made changes to. Just go through the different versions until you find the one you want.
BTSync saves 30 days' worth of version history by default. You can change the duration by clicking on the Properties tab in BTSync window and then clicking Advanced. In the advanced preferences window, select sync_trash_ttl. You'll see the number "30" appear in a Value text-entry field at the bottom of the window. Change that number to whatever the number of days you'd like BTSync to save version histories for, click the Set button, and close the window.
While BitTorrent Sync is built around syncing entire folders rather than individual files at this point, you can force it to ignore specific files in a folder, which could be handy in sharing situations.
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