How to fix an unknown error occurred (−1) − iPhone, iPad, iPod touch (iPhone)

Maybe your iTunes version is not the latest one available and it has a bug, which might have been resolved in the latest version. You can check for updates from inside iTunes, or on Apple's website.

Maybe your computer or iOS device are temporary blocked, e.g. by a temporary process initiated by the antivirus software.

Try restarting the computer and the iOS device and then restoring them.

Maybe iTunes failed to connect to your device properly, which is why you get the -1 error message. Try to restart it, by closing it and reopening it, and then try again.

Another reason for the "an unknown error occurred (-1)" error message is incorrect date and time settings. Ensure that you set the correct time and date on your computer and mobile device, and then rerun the process.

If you are not sure how to update the date and time, the don't know how to set the time and date guide will be of great help.

Maybe the current firewall and antivirus settings are responsible for the "an unknown error occurred (-1)" error message. As a test, try disabling them and check if you still get the error message. If the error message didn't appear, access the firewall and the antivirus and see how they are configured. If you are not sure how to access the antivirus, check the FAQ section from the manufacturers.

To disable the Windows Firewall:

To enable the Windows Firewall:

Maybe the reason for the an unknown error occurred (−1) error message is an outdated driver. It's very important to check for and update your computer's drivers on time, to prevent future bugs.

If you aren't sure how to find and install the appropriate drivers for your computer, check out the don't know how to download and install drivers.

Maybe a virus affected files associated with iTunes and is responsible for the unknown error -1. Scanning for and removing the viruses should be all you need to do, in order to fix the issue.

To learn how to scan for and remove viruses, check out the computer virus protection guide.

Updating the operating system is a must, in order to improve the device's functionality and eliminate bugs. Usually, the updates are being applied automatically, but sometimes this is not the case.

Feel free to check out the don't know how to update my device's operating system guide if you are not sure how to check for updates manually.

It is possible that an outdated antivirus software is the reason for this error message. To fix this, check if an update for your antivirus software is available on the developer's website, or from inside the antivirus (usually Settings > Help/Update > Check for updates) and if there is an update available, install it.

It is possible that dust lump that has accumulated in the computer's USB port and the iOS device's lightning port, is responsible for the error message, as it interrupts the strong link between your device and the computer. Double-check and clean the ports on both ends and try again.

Maybe the lightning cable itself is the reason why you keep getting the an unknown error occurred -1 error message. Repeat the same procedure, but this time using another lightning cable.

It is possible that unstable connection between the computer and the iOS device is responsible for error message -1. Disconnect and reconnect the USB cable on both ends and then try again.

Fake lightning cables can be responsible for many errors in the communication between your computer and iOS device. Ensure that your cable is the original one and try again.

Make sure to use original cables only, bought from an authorized store.