The stages and what each costs
A major update runs through four phases. The download takes a few minutes on good Wi-Fi and much longer on a weak connection. Preparing Update verifies and stages the new system and typically runs 10 to 20 minutes, longer on a device with a lot of data. Installing takes another 10 or so, with the Apple logo and a progress bar. First boot adds a few minutes before the Home screen appears.
A point release — 27.1 rather than 27.0 — is much quicker throughout, often under ten minutes end to end.
Older iPhones take longer, and that is normal
An iPhone 11 or an iPhone SE has slower storage and less memory than a current model, and every stage stretches. Forty-five minutes on a six-year-old device with a full library is not a fault.
Our per-model pages set out what to expect on each specific iPhone, including how much of the slowdown is the chip and how much is the storage.
When 'Preparing Update' has actually stalled
This is the stage people give up on too early. Twenty minutes with no visible movement is still within normal, and interrupting it is how a straightforward update becomes a recovery-mode restore.
The signal that something is genuinely wrong is a progress indicator that has not moved in over an hour and a device that is cold to the touch. A warm phone is still working. Our guide to this stage covers what to do at that point.
The first day afterwards
Once the Home screen appears the update is finished, but the phone is not. Spotlight reindexes everything on the device and Photos re-analyses your whole library, both CPU-intensive, and on a large library that work runs for hours.
That is why the day after an update feels slower and the battery drains faster. It settles by itself within two to four days. Leaving the phone on power and on Wi-Fi overnight gets it done faster, because iOS schedules that work aggressively when charging and idle.
How to make it faster
Free space more than anything else: a device with plenty of room stages the update far more quickly than one scraping the minimum. Good Wi-Fi and mains power do the rest.
Updating from a computer is meaningfully quicker on a constrained device, because the unpacking happens off the phone — see our computer update guide.
Frequently Asked Questions
How long should an iOS update take?
Roughly 15 to 30 minutes for a major release on a recent iPhone, and often under ten for a point release. Older devices take longer.
Why is Preparing Update taking so long?
It verifies and stages the whole new system, which takes 10 to 20 minutes normally and longer on a device with a lot of data. Under an hour is still normal.
Is it safe to interrupt an iOS update?
No. Interrupting the install is the main way a routine update turns into a recovery-mode restore. Leave it alone unless it has been static for over an hour and the phone is cold.
Why is my iPhone slow after updating?
Spotlight and Photos are reindexing in the background. It resolves on its own within two to four days.