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

Why does iTunes error -1 occur? How to fix it?

The device cannot be synced − an unknown error occurred (-1) popup in iTunes appears when you try to update or restore your iPhone, iPad or iPod touch via iTunes, using your computer.

The common reasons behind this error include:

  • Outdated iTunes version;
  • Outdated operating system;
  • Damaged iTunes files;
  • Malicious software.

We put together a list of solutions that should fix this error, if read them carefully, and follow the instructions.

Select specifications which apply:

Click on this if you use an iPhone.

Click on this if you tried all the other solutions and none of them worked.

Click on this if you use an iPad.

Click on this if you use an iPod touch.

  1. Update your iTunes to the latest version

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  2. Restart both the computer and your iOS device

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  3. Restart iTunes

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  4. Ensure that the correct date and time are set

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  5. Double−check the firewall and antivirus settings

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  6. Update the computer drivers (Windows)

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  7. Scan your computer for malicious software

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  8. Update the computer's operating system

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  9. Update your antivirus software

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  10. Ensure that the computer's USB port and the device's lightning port are clean

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  11. Use another lightning cable

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  12. Check if the USB (lightning) cable is firmly connected on both ends

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  13. Use an original lightning cable

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