Doing so requires tinkering with the ".SyncIgnore"file that appears when you enable hidden files in a synced folder (just like .SyncArchive). Open .SyncIgnore in your text editor of choice; Notepad works. Start a new line in the .SyncIgnore file and type the name, including the extension, of the file you want BTSync to ignore, such as example.doc or example.jpg. If you want to ignore multiples files, create a new line for each. Don't forget to save the file when you're done!
Now for the caveat: .SyncIgnore will force BTSync to ignore this file for all devices, including your own. If you want to share specific files with some people but not others, you'll have to create new folders for them and share the data normally.
Become truly cloudless
BitTorrent sync advertises itself as a cloudless option that lets you sync files without using a third-party server, but there are special situations where BTSync will use what's known as a relay server to send a file between two client PCs. This usually happens if one side is behind a firewall or there's some other technical reason that's preventing the two devices from sharing files. In these cases, your files are uploaded to a BitTorrent server during transfer, though the company says your files are scrambled with AES 128-bit encryption, preventing BitTorrent from seeing your files. Your files are deleted after the transfer is complete.
If you're not comfortable with that, however, you can disable the ability to connect to a relay server on a per-folder basis. To do this, select a folder, click the Info button and then select the Properties tab in the new window. Finally, uncheck the box that says "Use relay server when required."
Bam! Now you're free to enjoy the benefits of the cloud with any of its service outages — or privacy concerns.
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