Quick Summary
Error 1015 on iPhone primarily indicates an issue during the restore process, especially when trying to downgrade the iOS version. This error commonly occurs because the device is attempting to install an older iOS version that is no longer being signed by Apple, triggering Apple's anti-downgrade mechanism.
Common Causes
- Downgrade Attempt When SHSH Blobs are Missing: Apple requires valid SHSH blobs (digital signatures) for iOS versions to be installed. Trying to downgrade to an iOS version without its corresponding SHSH blobs (or with invalid blobs) triggers Error 1015, as the device cannot verify the firmware's authenticity.
- Baseband Incompatibility Issues: Sometimes, attempting to restore to a custom or modified IPSW (iPhone Software) file can lead to baseband incompatibility or corruption, which can manifest as Error 1015 during the restore process. This is because the bootloader is unable to load the old baseband version.
- Damaged or Corrupted IPSW File: A corrupted or incomplete IPSW file may result in incomplete or incorrect data being written during the restore process, which can trigger Error 1015. This can happen during the IPSW download.
- iTunes Glitches: Occasional glitches within iTunes during the restore process can manifest as various errors, including Error 1015. Outdated iTunes or conflicting software can contribute to this.
- Hardware Problems (Less Likely): While less common, underlying hardware issues within the iPhone itself, such as storage or connection problems, can sometimes lead to unexpected restore errors that may include Error 1015.
Step-by-Step Fixes
Method 1: Attempt to Restore to Latest Signed iOS Version
Step 1: Ensure you are using the latest version of iTunes or Finder (if using macOS Catalina or later).
Step 2: Put your iPhone into recovery mode. To do this on iPhone 8 or later: Press and quickly release the Volume Up button. Press and quickly release the Volume Down button. Then, press and hold the Side button until you see the recovery-mode screen. For iPhone 7 and 7 Plus: Press and hold both the Side (or Top) button and the Volume Down button at the same time. Keep holding them until you see the recovery-mode screen. For iPhone 6s and earlier: Press and hold both the Home button and the Side (or Top) button at the same time. Keep holding them until you see the recovery-mode screen.
Step 3: Connect your iPhone to your computer while in recovery mode. iTunes/Finder should prompt you to Restore or Update.
Step 4: Choose "Update" first. If that fails to resolve the issue, try "Restore". Be aware that restoring will erase all data on your iPhone if you do not have a backup.
Step 5: iTunes/Finder will download and install the latest signed iOS version. If all goes correctly, the error should resolve. (Note: Attempting to specifically target an older iOS version will still trigger anti-downgrade protections).
Method 2: TinyUmbrella (If SHSH Blobs Available/Applicable)
Step 1: If you have saved SHSH blobs for the iOS version you are trying to restore to, you can try using TinyUmbrella (Disclaimer: this method is complex and has varying success rates, especially on newer devices and iOS versions).
Step 2: Download and run TinyUmbrella.
Step 3: Put your iPhone into Recovery Mode or DFU Mode.
Step 4: Start the TSS server within TinyUmbrella to serve the SHSH blobs to your device.
Step 5: Attempt the restore process through iTunes again, pointing it to the older IPSW file.
Step 6: Important Note: Modern iOS versions have significantly enhanced protections against SHSH blob spoofing, which often renders methods using TinyUmbrella ineffective. This method is mostly only useful if previous attempts to store SHSH blobs have been successful, and may not work on newer iOS versions.
Method 3: Verify and Re-download IPSW File
Step 1: Ensure that the IPSW file you are using is not corrupted.
Step 2: Re-download the IPSW file from a reputable source.
Step 3: Before attempting to restore, compare the MD5 or SHA checksum of the downloaded IPSW file with the checksum provided by the source to ensure file integrity. If you use a Mac, you can use the Terminal command "md5 filepath" in the same directory as the ipsw to confirm the MD5. On Windows, you can use a tool called "MD5 & SHA Checksum Utility".
Step 4: Attempt the restore process in iTunes/Finder again with the newly downloaded IPSW file.
Method 4: DFU Mode Restore (Advanced)
Step 1: Put your iPhone into DFU (Device Firmware Update) mode. The procedure varies based on your iPhone model:
- iPhone 8 and later: Press and quickly release the Volume Up button. Press and quickly release the Volume Down button. Then, press and hold the Side button until the screen goes black. Immediately press and hold both the Side button and the Volume Down button. After 5 seconds, release the Side button, but continue holding the Volume Down button until your computer recognizes the phone in DFU mode.
- iPhone 7 and 7 Plus: Press and hold both the Side (or Top) button and the Volume Down button at the same time. Keep holding them for about 10 seconds. Release the Side (or Top) button but continue holding the Volume Down button until your computer recognizes the phone in DFU mode.
- iPhone 6s and earlier: Press and hold both the Home button and the Side (or Top) button at the same time. Keep holding them for about 10 seconds. Release the Side (or Top) button but continue holding the Home button until your computer recognizes the phone in DFU mode.
Step 2: Connect your iPhone to your computer.
Step 3: iTunes/Finder should detect your iPhone in recovery mode.
Step 4: Restore your device - be aware that a DFU restore will erase the contents of the phone.
Step 5: Avoid selecting a specific, older IPSW file; let iTunes/Finder select and restore to the latest signed firmware. Trying to downgrade will likely result in error 1015 reappearing.