By Jenefey Aaron

Updated on 2025-04-24

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Fix iPhone

Best Way to Fix This Firmware Is Not Signed When Downgrading iOS

By Jenefey Aaron

2025-04-24 / Fix iPhone

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As Apple rolls out new iOS versions each year, it eventually stops signing older ones. So, when you try restoring your device, you may see the error: This firmware is not signed. this means you cannot restore to it in iTunes. This can be frustrating, especially if the new update causes battery drain, overheating, or Bluetooth issues. Downgrading to an earlier, stable iOS version is often the best solution. In this guide, we’ll show you how to downgrade smoothly even if the firmware is unsigned by Apple.

Part 1: What Does "This Firmware Is Not Signed" Mean?

Part 2: Why Is My iPhone Firmware File Not Compatible or Corrupt?

Part 3: Best Way to Fix Unsigned Firmware Issue – Recommended Tool

Part 4: Can I Install or Restore Unsigned IPSW?

Part 5: Other 5 Methods to Fix "Firmware File Is Not Compatible/Corrupt"

Part 1: What Does "This Firmware Is Not Signed" Mean?

When you see the message "this firmware is not signed," it means that Apple has stopped authorizing or "signing" that particular iOS version. Every time you update or restore your iPhone using iTunes, Apple checks its servers to make sure the firmware you're using is still signed and allowed. Once a new iOS version is released, Apple usually stops signing older versions to prevent users from downgrading.

So, if this firmware is not signed, this means you cannot restore to it in iTunes the normal way. You’ll need special tools or saved SHSH blobs to install that version again.

Part 2: Why Is My iPhone Firmware File Not Compatible or Corrupt?

Seeing a message about a firmware file being "not compatible" or "corrupt" usually means something went wrong during the update or restore process. It usually happens because:

You downloaded the wrong IPSW file that doesn’t match your iPhone model.
Apple stopped signing that firmware, so iTunes won’t allow you to install it.
iTunes is outdated and can’t recognize the file.
Your internet connection was unstable while downloading, so the file got damaged.
Antivirus software or system settings blocked the process.

Part 3: Best Way to Fix Unsigned Firmware Issue – Recommended Tool

The easiest and most reliable way to fix the "this firmware is not signed" issue is by using Tenorshare ReiBoot. It’s a simple tool made for iPhone and iPad users who want to fix iOS bugs or go back to a previous iOS version without any hassle.

Whether you’re dealing with update glitches or want to downgrade from iOS 18 to iOS 17, ReiBoot has you covered. No technical skills are required, and the process is just a few clicks. It even works without needing SHSH blobs—a big plus for users who didn’t save them earlier.

How to Use ReiBoot to Downgrade iOS 18:

Download and install ReiBoot on your PC or Mac. Open the tool and connect your iPhone using a USB cable. Click on "iOS Upgrade/Downgrade."
Choose the "Downgrade" option and confirm to move ahead.
ReiBoot will detect your device and suggest the right firmware. Click "Download" to get it.
After the download finishes, click "Initiate Downgrade." ReiBoot will begin the downgrade safely.
Once done, click "Done." Your iPhone will restart with the older iOS version fully installed.

Part 4: Can I Install or Restore Unsigned IPSW?

Many users wonder if it's possible to install or restore an unsigned IPSW file after seeing the message: "This firmware is not signed. This means you cannot restore to it in iTunes."

Apple uses a signing system to control which iOS versions can be installed on your device. Once a new iOS version is released, Apple usually stops signing the older ones, making it impossible to install them through iTunes the traditional way. That’s why when you try to downgrade using an old IPSW, iTunes shows that error message.

So, is it still possible?

Yes, but not with iTunes alone. You need advanced tools like Tenorshare ReiBoot or 3uTools, and sometimes SHSH blobs (saved digital signatures) to make it work. These tools allow you to bypass Apple’s signing restrictions and restore unsigned firmware safely.

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Part 5: Other 5 Methods to Fix "Firmware File Is Not Compatible/Corrupt"

You can also try some basic manual solutions if you don't want to use a third-party tool like ReiBoot. These methods can help fix compatibility or corruption issues with firmware files during restore or update processes in iTunes.

1. Restart Computer and iTunes

A simple restart can fix minor glitches that cause firmware compatibility issues. Restarting both your computer and iTunes refreshes the system and often resolves hidden software conflicts.

Close iTunes completely.
Restart your computer.
Open iTunes again.
Reconnect your iPhone and try the restore/update again.

2. Disable Antivirus or Firewall

Security software can sometimes block firmware file downloads or interfere with iTunes. Disabling your antivirus or firewall temporarily can allow the process to complete successfully.

Steps:

On Windows, right-click your antivirus icon in the system tray.
Choose "Disable temporarily" (select 15–30 mins).
Go to Control Panel > System and Security > Windows Defender Firewall > Turn off Windows Firewall.

Open iTunes and connect your iPhone.
Try restoring or updating the device.

3. Update or Reinstall iTunes

Older or broken iTunes versions may not recognize the latest firmware formats. Keeping iTunes up to date ensures compatibility with Apple’s latest IPSW files.

Option A: Update iTunes

Open iTunes.
Click Help > Check for Updates (Windows) or update via the App Store (Mac).

Install the available update.
Restart iTunes and try again.

Option B: Reinstall iTunes

Uninstall iTunes from your system.

On Windows: Go to Control Panel > Programs > Uninstall a program.

Download the latest version from Apple’s official site.
Reinstall and restart your system.
Reconnect your device and retry the update/restore.

4. Manually download correct IPSW file

Sometimes iTunes downloads the wrong IPSW or fails to fetch it completely. Manually downloading the right version gives you more control.

Visit https://ipsw.me.
Select your iPhone/iPad model.
Download a signed firmware version (green-highlighted).
Open iTunes and connect your device.
Press:

Shift + Restore (Windows)

Option + Restore (Mac)

Select the IPSW file you downloaded.

Proceed with the restore.

5. Restore via DFU Mode

DFU (Device Firmware Update) mode allows the deepest level of restore, skipping many software-level checks. It’s a powerful way to fix even serious firmware issues.

Connect your iPhone to the computer via USB.
Put your device into DFU mode:
Press and quickly release Volume Up, then Volume Down.
Press and hold the Side button until the screen turns black.
While holding the Side button, press and hold Volume Down for 5 seconds.
Release the Side button but keep holding Volume Down for another 10 seconds.
The screen should remain black, and iTunes will say your iPhone is in recovery mode.
Click Restore in iTunes.

Follow the prompts to complete the process.

Final Words:

Seeing the message this firmware is not signed. this means you cannot restore to it in iTunes can be frustrating. Apple’s signing restrictions make it difficult to install older iOS versions using traditional methods like iTunes. But don’t worry; you’re not stuck.

With tools like Tenorshare ReiBoot, you can safely downgrade to unsigned iOS versions or fix firmware compatibility issues without relying on iTunes or SHSH blobs. It’s fast, simple, and doesn’t require technical skills. Whether you're facing update glitches, want to roll back to a previous version, or simply need a smoother iOS experience.

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