iPhone backup or sync issue "unknown error occurred (-50)"

I recently switched from iCloud backup to backing up to my computer since the iOS 8 update seems to have doubled the size of my backup and it no longer fits on iCloud.

When backing up to my computer by pushing "Back Up Now" in iTunes, I get an error message:

The iPhone 'X' cannot be synced. An unknown error occurred (-50)

The last backup time does change, and it isn't saying that the backup failed, but it is odd that I get that error every time.

I am telling it to not backup any of the apps, because I don't want all that dead space on my laptop. The error seems to happen after the backup and when the sync process changes to "Transferring purchases from X"

I searched around and wasn't able to find a satisfying definition of error -50 does anyone know what it is?

I got this error just now. My Mac mini was connected to my LAN via WiFi and also via Ethernet. That was working ok, but I was trying to get the phone to sync via Wifi (still can't get that working).

Anyway, I pulled out the Ethernet cable. Plugged the phone in via USB and when I clicked Sync I got the (-50) error you describe.

My solution was to exit iTunes, and then launch it again. This was enough to get the phone syncing with no error.

This is my fix, for iPhone 6 iOS 8.4 2015 My problem was caused by a dummy app, I removed it through iPhone's SETTING, GENERAL, USAGE, MANAGE USAGE. Look for empty app name or blank icon. Remove the app. Try to backup again, if fail again, check for the LOG of your iTunes.

For Windows, go to

1. C:\Users\XXXXXX\AppData\Roaming\Apple Computer\Logs
2. Open the log, and see what's the problem. For my case there problem was [11132 @ Fri Oct 09 21:27:23 2015] [com.apple.console AppleMobileBackup.exe] ERROR: Backup message response: 101 Unable to open domain directory: No such file or directory (2) at path "/var/mobile/Containers/Shared/AppGroup/8E726549-3ED1-4171-818A-12B66843C156" (MBErrorDomain/101)
3. For my case, this App " 8E726549-3ED1-4171-818A-12B66843C156" caused the problem. So I just browse into my iPhone's directory using iExplorer, and create a folder with the same name. Note: My iPhone is jailbroken. Then I manage to backup my phone.

Note: If you see similar error message, thats mean it's caused by an APP. Just try to delete more app and try to backup again. Good Luck!

This happened to me too. As user110611 suggested, I quit iTunes then relaunched it, with my iPhone still connected to the USB port. It began syncing immediately after that.