Apple iPhone Error Code 21: How to Fix It
Medium 30-90 minutes High Severity
Verified June 2026
- Error Code
- 21
- Brand
- Apple iPhone
- Product Type
- mobile
- Severity
- High
- DIY Difficulty
- Medium
- Estimated Fix Time
- 30-90 minutes
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Tools You'll Need
- Computer with iTunes installed
- Original Lightning cable
- Power adapter
How to Fix Error Code 21
-
Check Battery Level and Charge Device
Always use genuine Apple charging cables to avoid data transfer issues during restore. -
Update iTunes and Computer
-
Try Different USB Port and Cable
Avoid using USB hubs or extension cables as they can cause data transfer interruptions. -
Put iPhone in Recovery Mode
Do not release buttons until you see the recovery mode screen with iTunes logo. -
Attempt iTunes Restore in Recovery Mode
Do not disconnect your iPhone during the restore process as this can cause permanent damage. -
Try DFU Mode if Recovery Mode Fails
DFU mode screen will be completely black. If you see any logos, restart the process. -
Use Different Computer
Temporarily disable antivirus software during the restore process as it may interfere with iTunes. -
Check for Hardware Issues
Do not attempt to open your iPhone or perform hardware repairs yourself as this voids warranty and can cause further damage.
Parts You May Need
Lightning charging cable
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USB power adapter
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Lightning charging cable
Check Price on Amazon
USB power adapter
Check Price on Amazon
Lightning charging cable
Check Price on Amazon
USB power adapter
Check Price on Amazon
Lightning charging cable
Check Price on Amazon
USB power adapter
Check Price on Amazon
Lightning charging cable
Check Price on Amazon
USB power adapter
Check Price on Amazon
Lightning charging cable
Check Price on Amazon
USB power adapter
Check Price on Amazon
Lightning charging cable
Check Price on Amazon
USB power adapter
Check Price on Amazon
Lightning charging cable
Check Price on Amazon
USB power adapter
Check Price on Amazon
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When to Call a Professional
Contact Apple Support or visit an Apple Store if Error 21 persists after trying all software solutions, especially if your iPhone is still under warranty. Professional diagnosis is needed for hardware-related issues like logic board failures or flash memory corruption that require specialized tools and expertise.Frequently Asked Questions
What does iPhone Error Code 21 mean?
iPhone Error Code 21 indicates that iTunes failed to restore your device during DFU mode. This typically happens due to low battery, hardware faults, corrupted firmware, or communication issues between your iPhone and iTunes.
Can I fix Error 21 without losing my data?
Unfortunately, Error 21 usually occurs during restore processes, which erase all data on your iPhone. If you have a recent backup in iTunes or iCloud, you can restore your data after fixing the error. Always backup regularly to prevent data loss.
Why does my iPhone keep getting Error 21?
Recurring Error 21 often indicates hardware problems such as a failing flash memory chip, damaged dock connector, or logic board issues. After ruling out software causes, professional diagnosis is recommended to identify the specific hardware fault.
Is iPhone Error 21 the same as iTunes Error 21?
Yes, iPhone Error 21 and iTunes Error 21 refer to the same issue. The error appears in iTunes when trying to restore an iPhone, indicating a communication failure during the restore process.
How long should I charge my iPhone before trying to fix Error 21?
Charge your iPhone for at least 30 minutes before attempting any restore process. A battery level below 50% can cause Error 21, so ensure adequate power throughout the restore procedure.