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Software Modification Issues High Severity

Error 1015: Unauthorized Software Modification

This error occurs when your device has unauthorized software modifications (jailbreaking) or when you are trying to install an earlier version of iOS (downgrading).

Before You Begin
  • • On Mac with macOS Catalina 10.15 or later: Ensure your Mac is up to date
  • • On Mac with macOS Mojave 10.14 or earlier: Ensure you have the latest version of iTunes
  • • On PC: Ensure you have the latest version of iTunes or the Apple Devices app
Warnings
  • 1 You cannot downgrade to an iOS version Apple is no longer signing
  • 2 Jailbroken devices may lose data during restore
  • 3 Always backup your device before attempting restore
Common Causes
  • 1 Device has been jailbroken
  • 2 Attempting to downgrade iOS to an earlier version
  • 3 Unauthorized software modifications detected
  • 4 Custom firmware installed on device
Detailed Guide

Understanding Error 1015

Error 1015 occurs when your device has unauthorized software modifications (typically a jailbreak) or when you are trying to install an earlier version of iOS (downgrading). Apple’s restore servers reject the request because the target iOS version is either unsigned or the device’s software state is not legitimate.

Why Error 1015 Happens

  • Jailbroken device: Custom firmware or modified system files are detected
  • Downgrading: Attempting to install an older iOS version that Apple is no longer signing
  • Custom IPSW: Using a modified IPSW file instead of the official Apple firmware

Step-by-Step Troubleshooting

1. Use Recovery Mode to Restore to Latest iOS

The only supported way to resolve Error 1015 is to restore your device to the latest signed iOS version:

  1. Connect your device to the computer
  2. Enter recovery mode
  3. iTunes/Finder will detect the device in recovery mode
  4. Click Restore — this will install the latest iOS version
  5. Your device will be wiped clean, so restore from backup afterward

2. Try DFU Mode

If recovery mode doesn’t work (sometimes jailbreaks interfere with recovery mode):

  1. Enter DFU mode instead
  2. iTunes/Finder will detect a device in recovery state
  3. Click Restore to install the latest iOS version

Before restoring, remove any jailbreak tools from your computer:

  • Delete custom IPSW files
  • Remove any hosts file modifications (see Error 3194 for details)
  • Uninstall jailbreak utilities (TinyUmbrella, redsn0w, etc.)

4. Edit the Hosts File

If you’ve used jailbreak tools, they may have modified your hosts file to redirect Apple’s servers:

On macOS:

  1. Open Terminal and type: sudo nano /private/etc/hosts
  2. Remove or comment out any lines containing gs.apple.com

On Windows:

  1. Open Notepad as Administrator
  2. Open C:\Windows\System32\drivers\etc\hosts
  3. Remove or comment out any lines containing gs.apple.com

Important Notes

  • Downgrading is not possible once Apple stops signing an iOS version. Check our signing status page for current signing status
  • Data loss: Restoring from a jailbroken state will erase all data. Back up your device before attempting a restore
  • Re-jailbreaking: After restoring to the latest iOS, your device will no longer be jailbroken. You cannot selectively keep jailbreak tweaks

Related Articles

Article

How to Downgrade iOS Using IPSW

Article

Resolving Common IPSW Installation Errors

Article

How to Enter Recovery & DFU Mode on iPhone

Important Notes
  • You cannot downgrade to an earlier iOS version
  • Jailbroken devices may lose data during restore
  • Always backup your device before attempting restore

Other Software Modification Issues

RES
Error

The Required Resource Can't Be Found

Still Need Help?

If you've tried all the steps above and still can't resolve the issue, you may need to contact Apple Support or visit an Apple Store. You can also compare your case against Apple's official iOS update and restore errors page.

More Troubleshooting Tips Recovery Mode Guide