When you instruct your phone to download and install this update, it connects to Apple servers to begin the patching process. The screen displaying the message “Preparing Update” generally means just that, your phone is preparing the update file for download and installation.

How long should iPhone say preparing update?

I suggest allowing at least 30 minutes, maybe more depending on what else is happening on the network.

Why is my iPhone stuck on preparing update?

One of the reasons why your iPhone is stuck on preparing an update screen is that the downloaded update is corrupted. Something went wrong while you were downloading the update and that caused the update file not to remain intact.