iOS Update Error: Causes and Step-by-Step Fix

What Error 4013 Means

A system failure during an iOS update installation occurs when the update process cannot verify the package's digital signature, extract the archive, or write files to the system partition. On the screen, you will see a message such as Could Not Install Update or An error occurred while verifying the update. The process halts during the preparation or installation phase, leaving the device running on its current firmware version.

This error frequently occurs during over-the-air (OTA) updates but can also appear when connecting to a computer. The issue is non-critical: user data remains intact. However, repeatedly attempting the update without changing the conditions will only result in further failures.

Common Causes

• Unstable internet connection. Wi-Fi dropouts or using public networks with traffic restrictions can interrupt the download of large update archives.
• Insufficient storage space. Extracting and applying an iOS update requires a temporary buffer of 5 to 10 GB. If storage is full, the process will terminate unexpectedly.
• Corrupted update file. Interrupted downloads or caching failures can cause the system to attempt installing a corrupted archive.
• Outdated computer software. Older versions of iTunes, Apple Devices, or macOS Finder lack the necessary drivers to properly write new iOS versions.
• Profile or modification conflicts. Installed developer beta profiles, enterprise certificates, or remnants of a jailbreak can interfere with system integrity checks.

Troubleshooting Steps

Method 1: Check Network Connection and Free Up Storage

Start with basic diagnostics. Ensure your wireless router is operating on the 5 GHz band and that you have a strong signal (at least two bars).

1. Go to Settings → Wi-Fi and verify that the connection is active. Temporarily disable Cellular Data.
2. Navigate to Settings → General → iPhone Storage.
3. If storage usage exceeds 85%, delete unused apps, clear messenger caches, or remove old videos.
4. Ensure at least 5 GB of free space remains, then retry the update.

💡 Tip: If the update starts but appears stuck on the progress bar, do not turn off the device. The extraction process can take up to 30 minutes.

Method 2: Delete the Corrupted Update Package

The system often saves a partially downloaded file and attempts to install it again, which guarantees the error will recur. You need to clear it.

1. Go to Settings → General → iPhone Storage.
2. In the app list, locate the entry for the current update version, such as iOS 17.5.
3. Tap it and select Delete Update.
4. Restart the device via Settings → General → Shut Down.
5. After it powers back on, return to Settings → General → Software Update and start the download again.

Method 3: Force Restart and Reset Network Settings

Occasionally, the issue is caused by a corrupted network stack or a stalled background update process.

1. Perform a force restart: quickly press and release Volume Up, then quickly press and release Volume Down, then press and hold the side button until the Apple logo appears.
2. Go to Settings → General → Transfer or Reset iPhone → Reset.
3. Select Reset Network Settings. This will erase saved Wi-Fi passwords but will clear potential network conflicts.
4. Connect to your home router and attempt the system update again.

Method 4: Update via Computer (Most Reliable)

If OTA methods fail, connecting to a PC bypasses the limitations of the mobile update client and utilizes a stable USB connection.

1. Connect your iPhone or iPad to the computer using an original or MFi-certified cable.
2. On macOS, open Finder; on Windows, open the Apple Devices app or iTunes. If prompted, tap Trust on your device's screen.
3. Select your device from the sidebar.
4. Hold down the Option key (macOS) or Shift key (Windows) and click the Update button.
5. Confirm the action. The computer will download a fresh system image and install it over your existing data.

⚠️ Important: Do not disconnect the device during the process. Unplugging the cable during the write phase can corrupt the system partition.

Prevention Tips

To ensure smooth updates in the future, follow these best practices:

• Keep 10–15 GB of free storage available. While iOS automatically reserves space for extraction, critically low storage levels often cause failures.
• Only update over a stable home Wi-Fi network. Avoid public networks, hotel hotspots, and cellular data when downloading large packages.
• Keep your computer software up to date. Newer versions of Finder/iTunes include USB driver fixes and compatibility patches for the latest firmware.
• Do not manually interrupt the process. Even if the screen turns off, the device continues working in the background. Keep it connected to a charger and allow the operation to complete.