First: is an update actually available for your model?
Software Update never offers a version your iPhone cannot run. If nothing appears, the most likely explanation is not a fault — it is that your model has reached its last supported version, or that you are already on the newest one. Check Settings → General → About against what you expected.
Our compatibility checker answers this for your exact model in one step. If your iPhone has reached the end of its road, our guide for older iPhones explains what still matters.
Free space, which fails later than you expect
The installer checks free space when it installs, not when it downloads — which is why the failure so often arrives after a long download has finished. It needs roughly twice the download size available, around 15 GB for a major release.
Settings → General → iPhone Storage gives the real number and the fastest fixes. Offloading a few large apps returns their space immediately while keeping their data. Our storage guide covers the rest.
A corrupted download
If the progress bar stops at the same point every attempt, the downloaded file is damaged and iOS will not tell you so. Delete it: Settings → General → iPhone Storage, find the iOS update in the app list, tap it and choose Delete Update. Restart, then download again.
Captive-portal networks — hotels, offices, universities, anything with a sign-in page — corrupt large downloads regularly. Retrying on a different network is often the whole fix.
"Unable to Verify Update"
This message means the iPhone could not confirm the update with Apple's servers. It is usually transient: restart the phone and try again, and check that the date and time are correct under Settings → General → Date & Time with Set Automatically turned on. A wrong clock breaks certificate validation and produces exactly this error.
If it persists, delete the downloaded update as above and start over. Our full guide to this error covers the remaining causes.
Restrictions you may not know are there
A work or school iPhone can be blocked from major updates by a mobile device management profile. Settings → General → VPN & Device Management shows whether one is installed. The restriction is set by the organisation and cannot be removed from the device.
Screen Time can also block updates: Settings → Screen Time → Content & Privacy Restrictions. And if Software Update shows an update but the install button does nothing, check that Automatic Updates has not already staged and scheduled it for overnight.
When to use a computer instead
Updating through Finder on a Mac or the Apple Devices app on Windows sidesteps most of the above — the computer downloads and unpacks, so both the space requirement and the on-device download problems largely disappear. It is the right move once an over-the-air update has failed twice.
If the phone will not boot far enough to update at all, recovery mode and a restore from a signed IPSW is the last resort; it erases the device, which is why the backup matters. Our IPSW guide covers it.
Frequently Asked Questions
Why does my iPhone say no update available?
Most often because your model has reached its last supported version, or you are already current. Rollouts are also staged over several days for major releases.
Why does my iPhone update keep failing?
Free space and a corrupted download are the two common causes. Delete the update in iPhone Storage, restart, free up space and try again on a different network.
What does 'Unable to Verify Update' mean?
The iPhone could not confirm the update with Apple. Check that the date and time are set automatically, restart, delete the staged update and retry.
Can my employer stop my iPhone updating?
Yes. A management profile can block major version updates, and on a supervised device that restriction cannot be removed from the phone.