iOS 18 updates typically take 15 to 45 minutes on most iPhones, though the time depends on your device model, internet speed, and available storage
The actual read and installation happen in stages, and each stage has its own timing. Your phone downloads the update file (usually 3 to 6 gigabytes), verifies it, installs it to the system partition, and then restarts. A fast Wi-Fi connection and a phone with plenty of free space will finish in under 30 minutes. A slower connection, an older iPhone, or a device running low on storage can stretch the process to an hour or more.
The time also depends on whether you update while plugged in and whether your phone is actively in use. Apple's system works fastest when your iPhone is connected to power, on Wi-Fi, and left alone — ideally overnight or during a time you are not using it. If you interrupt the process or unplug the phone, the update will pause and restart from where it left off, adding time.
Key Takeaways
- Most iOS 18 updates finish between 15 and 45 minutes, but older iPhones and slower internet connections can take an hour or longer.
- Plugging your phone into power and using a strong Wi-Fi connection cuts update time significantly compared to updating on cellular data.
- Your iPhone needs at least 5 to 7 gigabytes of free storage before the update begins, or the installation will fail partway through.
- Restarting your phone or losing internet during an update pauses the process, and it will resume from that point when conditions improve.
Why the timing varies between devices
Older iPhones — particularly the iPhone XS, iPhone 11, and iPhone 12 — process updates more slowly than newer models because they have slower processors and less RAM. An iPhone 15 or iPhone 16 will typically finish in 20 to 30 minutes, while an iPhone 11 might take 40 to 50 minutes for the same update. The difference is not dramatic, but it is noticeable.
Storage speed also matters. iPhones with full or nearly full storage take longer because the phone has to shuffle files around to make room for the update. If your iPhone has less than 5 gigabytes free, the update may fail entirely and ask you to delete photos, videos, or apps before trying again. Clearing out old photos or unused apps before you update can cut several minutes off the total time.
How internet speed affects the read phase
The read portion — where your phone pulls the update file from Apple's servers — is the stage most affected by your connection. On a strong home Wi-Fi network (50 Mbps or faster), the read typically takes 5 to 10 minutes. On a weaker Wi-Fi signal or a slower connection, it can take 15 to 20 minutes or longer.
Cellular data is significantly slower for large files. If you update over LTE or 5G, the read alone can take 30 to 45 minutes, and your phone may time out if the connection drops. For this reason, Apple recommends Wi-Fi for all updates. If you must update on cellular, use 5G if available, keep your phone in one location with a strong signal, and do not use other apps while the update is running.
What happens during the installation and restart
After the read finishes, your iPhone verifies the update file to make sure it was not corrupted during transfer. This verification step takes 2 to 5 minutes. Then the phone installs the new system files, which takes another 5 to 15 minutes depending on your device. Finally, your iPhone restarts, which usually takes 2 to 3 minutes.
During the restart phase, you will see the Apple logo on a black screen. This is normal and does not mean anything went wrong. Do not force-restart your phone or unplug it during this time. If the restart takes longer than 10 minutes, something may have gone wrong — but wait at least 15 minutes before assuming the update failed.
How to speed up an iOS 18 update
Plug your iPhone into power before you start. Updates run faster when the phone is charging because the processor can work at full speed without worrying about battery drain. Use a wall outlet rather than a computer USB port, which delivers power more slowly.
Connect to a strong Wi-Fi network. Move closer to your router if the signal is weak, or switch networks if you have access to a faster one. Close all other apps and do not use your phone while the update is running — background activity slows down the installation process.
Free up storage space before you begin. Delete old photos and videos you have already backed up to iCloud, remove apps you no longer use, or clear your browser cache. Aim for at least 10 gigabytes of free space to give the update room to work without slowdowns.
Update during off-peak hours if possible. Late evening or early morning, when fewer people are downloading updates from Apple's servers, may result in faster downloads. This is a minor factor compared to your own internet speed, but it can shave a few minutes off the total time.
What to do if the update takes longer than expected
If your update is still running after 90 minutes, something may have stalled. First, check that your phone is still connected to Wi-Fi and plugged in. If the connection dropped, the update will pause and resume when the connection returns.
If the phone is connected and plugged in but still stuck on the same screen after 15 minutes, try restarting your Wi-Fi router. Unplug it for 30 seconds, plug it back in, and wait for it to reconnect. Then check whether your iPhone resumes the update.
If the update fails completely and your phone shows an error message, note the error code and try again on a different Wi-Fi network if possible. If the same error appears twice, your iPhone may have a hardware issue or a corrupted system file. At that point, contact Apple Support or visit an Apple Store, as the phone may need to be restored through a computer.
Frequently Asked Questions
Can I use my iPhone while it is updating?
No. Once the installation phase begins, your phone will be locked and unusable. You can use your phone normally during the read phase, but the moment you tap "Install Now" or the phone automatically begins installation, you should set it down and leave it alone. Using it during installation will slow the process and may cause the update to fail.
Will I lose my data if the update is interrupted?
No. If your phone loses power or internet during an update, the process will pause and resume from where it stopped once the connection or power returns. Your data is not at risk. However, the update will not complete until the phone finishes all stages, so you will not be able to use your phone normally until the update is done.
Why does my iPhone say it is preparing to update but nothing is happening?
The "Preparing Update" screen can last 5 to 15 minutes while your phone checks storage, verifies the read, and gets ready to install. This is normal. Do not force-restart your phone or unplug it. If it stays on this screen for more than 20 minutes, try restarting your Wi-Fi router and waiting another 10 minutes.
Is it safe to update overnight?
Yes. Plug your phone in, connect to Wi-Fi, and let it update while you sleep. This is actually the best time to update because your phone will not be interrupted, and you will not be tempted to use it during the process. Just make sure your phone is plugged into a wall outlet, not a computer, so it has steady power throughout the night.