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12 Ways to Fix Unable to Install Update. An Error Occurred Installing iOS 15

DoubtUser Concern

“Anyone else getting an error when trying to install iOS 15? I got an error saying 'Unable to install update. An error occurred installing iOS 15'. I retried like 5 times and always got the same error. Anybody got suggestions?”

Apple regularly releases iOS updates to fix bugs, add additional features or improve functions of iPhone, iPad and iPod touch. You can easily update your device wirelessly by going to Settings > General > Software Update.

However, when installing an iOS or iPadOS software update, some users got the error of "Unable to Install Update. An error occurred installing iOS 15". Don't panic. This is one of the most common iOS issues and there are are several ways to fix the problem on your own.

unable to install ios update error

Before troubleshooting, make sure you backup the iPhone or iPad in case something goes wrong during the update process:

  • Use iCloud: on your iPhone or iPad, go to Settings > [your name] > iCloud > iCloud Backup.
  • Use iTunes/Finder: Connect iPhone or iPad to your computer and open iTunes or Finder, select your device and click "Back Up Now".
  • Use Third-party Tool like FoneGeek Backup & Restore (iOS) to backup data on your iPhone or iPad more flexibly.

Once you made the backup, try out these solutions introduced below to resolve the Unable to Install Update error.

Tip 1. Check If Your iPhone Supports iOS 15

Please note that iOS 15 is no longer compatible with the iPhone 5s, iPhone 6 and iPhone 6 Plus. If you're unable to install iOS 15, please first check if your iPhone or iPad are on the supported list.

  • iOS 15 Supported Devices: iPhone 13, iPhone 12, iPhone 12 mini, iPhone 12 Pro (Max), iPhone 11, iPhone 11 Pro (Max), iPhone XS (Max), iPhone XR, iPhone X, iPhone 8 (Plus), iPhone 7 (Plus), iPhone 6s (Plus), iPhone SE.
  • iPadOS 15 Supported Devices: 12.9-inch iPad Pro, 11-inch iPad Pro, 10.5-inch iPad Pro, 9.7-inch iPad Pro, iPad (6th generation), iPad (5th generation), iPad mini (5th generation), iPad mini 4, iPad Air (3rd generation), iPad Air 2

Tip 2. Restart Your Device

Try to restart your iPhone, iPad and iPod touch sometimes does work to fix the issue of an error occurred installing iOS 15. And it can be the easiest step for you to take. Simply power off your device and then power on to see if it helps to solve the problem. If not, keep reading.

force restart iphone

Tip 3. Force Restart iPhone

If the above solutions don't work for you, do a force restart may be your best bet. Here's how to force restart your iPhone or iPad:

  • For iPad with Face ID, and iPhone 8 or later: Preas and quickly release the Volume Up button, then press and quickly release the Volume Down button. After that, press and hold the Side/Top button until you see the Apple logo.
  • For iPhone 7 models: Press and hold the Top/Side button and the Volume Down button at the same time until the Apple logo shows up.
  • For iPad with Home button, iPhone 6s and earlier: Press and hod the Side/Top button and the Home button together until the Apple logo appears.

force restart iphone

Tip 4. Ensure That iPhone Battery is Over 50%

To install the iOS update, you must ensure that the battery is more than 50%. If the battery is less than 50%, you can connect the device into charging and download the iOS update again when the battey is over 50%.

Tip 5. Check Network Connection

You need a good and stable internet connection to do the iOS update. Poor internet connection may interrupt the update process. So, check your network connection before installation:

  • Make sure you're on Wi-Fi and it is actively online. You can test this by opening Safari and visiting any website.
  • If possible, try to update your iPhone or iPad using a different Wi-Fi network.
  • Also, you can try to turn off WiFi and then turn it back on to refresh the internet connection
  • You can also try to reset network settings on your device by going to Settings > General > Reset > Reset Network Settings.

check wifi connection

Tip 6. Check Your iPhone Storage

The iOS 15 installation process may also be interrupt due to insufficient storage space on your device. In this situation, you should check the iPhone storage and make sure there is enough space to download and install an iOS update.

  • Firstly, go to iPhone's update page by clicking Settings > General > Software Update. Then the required storage to install iOS 15 will be displayed. You should ensure that the free space on your iPhone is more than the data size of the iOS update file.
  • Then go to Settings > General > iPhone Storage to check the used and free storage on your iPhone. You should clear iPhone caches, junk files and uncessary data if you found that there is no sufficient storage to update iOS 15.

check iphone storage

Tip 7. Wait for a While and Try Again

Once the new iOS 15 version is released to all Apple users, tens of thousands of users can hardly wait to have the new version downloaded and installed immediately. Then the problem arises.

Too much traffic on Apple server will definitely result in the failure of installing iOS update file. So we suggest you be patient to try again several hours or several days later.

Tip 8. Remove and Download the Update Again

If you still fail to install the iOS 15 update, try simply removing and downloading the update again. Here's how:

  • On your iPhone, go to Settings > General > iPhone Storage and locate the update in the list of apps.
  • Tap on the update and choose the option of "Delete Update".
  • Restart the device and then go back to Settings > General > Software Update to download the latest update again.

delete software update on iphone

Tip 9. Force Quit Settings App

Try to quit the Settings app if you still cannot install the iOS 15 update.

  • Swipe up from the bottom of the device and drag up the Settings app to force quit it.
  • Then click on Settings app on iPhone and go to General - Software Update to check if the new iOS update is listed here.

force quit settings app

Tip 10. Fix iOS Update Error without Data Loss

If "Unable to Install Update. An error occurred installing iOS 15" issue still appears after trying all the tricks, the best solution that is 100% work for you is using FoneGeek iOS System Recovery. It is easy to use and will never deleted or damage the current data stored on iPhone.

Besides this kind of iOS update issue, a wide range of other iOS issues can also be resolved, such as iPhone stuck on Apple logo, black screen, boot loop, etc.


This program is 100% secure to use and highly recommended by CNET, Software.Informer, Filehorse, GetDroidTips, Lera Blog and many other media sites. Advanced technology is also used to support all models of iPhone, iPad and iPod Touch.

Step 1. After you have downloaded FoneGeek iOS System Recovery on your computer, launch it and connect your device with an original cable. Then click "Standard Mode".

choose repair mode

Step 2. If your iPhone or iPad is not detected by the program, you can put the device into DFU mode as the instructions on the interface.

put iphone into recovery mode

Once the device is successfully put in DFU mode, the program will detect the device information and provide the newest firmware package. You can select the firmware of iOS 15 and click on "Download".

download firmware

Step 3. The program will begin to install the newest iOS firmware. Keep the device connected with the program and do no use it until the installation process is completed. Then restart your iPhone and check whether the iOS version is successful updated.


Tip 11. Update iOS with iTunes/Finder

You can also connect your device to a Mac or Windows PC and install the iOS update through iTunes or Finder. Here's what you need to do:

  1. Connect your iPhone or iPad to your computer using USB cable and launch iTunes or Finder.
  2. When iTunes/Finder detects the device, click on the device icon and tap "Check for Update" to install the new iOS update version.

check for update

Tip 12. Use IPSW to Install the iOS Update

You can also use the iOS IPSW file to update your iPhone or iPad. However, this method is only for those who are technologically advanced as the process is a bit more complicated.

  1. Download the IPSW file for your device on your computer.

  2. Connect your iPhone or iPad to the computer and launch iTunes or Finder.

  3. Hold down the Shift key in Windows or Alt/Option key on Mac and then click "Update".

  4. Then find and choose the IPSW file you just downloaded.


We have listed the 10 simple solutions above. Compared with other complicated tips, FoneGeek iOS System Recovery will be quite easy to remove the issue of an error occurred installing iOS 15. 

What's better, if you have any other errors after updating to iOS 15, you can also downgrade iOS 15 to iOS 14 without iTunes via this tool. If you have any better ideas or have opinions with this article, you can leave your comment below.

Fay J. Melton

Fay J. Melton has explored the area of technology and software for more than 5 years and he is enthusiastic about helping users solve various technology issues.

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