The progress bar creeps along and then stops. Or Finder throws up "an error occurred" and the whole backup is gone. Being unable to save a copy of your phone is worrying, especially before an upgrade, so let me walk this through with you.
These really are steps rather than alternatives. Apple's own page says to try the backup again after each one. So do them in order, and retry between each.
1. Update the computer before you touch the phone
Apple documents this as step one, and it is first here for the same reason.
Apple, in If you can't back up your iOS or iPadOS device to a computer: "Make sure your Mac or PC is up-to-date. Make sure that you have the latest version of the Apple Devices app or the latest version of iTunes."
A Mac several versions behind is the commonest reason of all. So is a Windows PC still on an old iTunes. A modern iPhone will not hand over a backup to either.
Retry the backup once the computer has updated. If it works, you are done here.
2. Take the phone off the hub and plug it straight in
Owners report this one and it costs nothing to test. It is the only confirmed fix I found.
An owner whose backup had failed for weeks found their iPhone was going through a USB hub. They plugged it straight into the machine's own socket. The backup completed.
So use the port on the computer itself. No hub. No dock. No monitor pass-through. Use an Apple cable if you have one, and swap ports if the first one fails.
⚠️ A charging-only cable powers the phone and carries no data. If the computer can see the phone at all, you are past that. It is still worth ruling out with a cable you know works.
3. Unlock, tap Trust, and answer any prompt on the phone
Apple's second step. Half of it happens on the handset rather than on the screen in front of you.
Apple, same page: "Connect your device to your computer with a USB cable, and locate your device on your computer."
Unlock the phone with the cable already attached. Tap Trust if it asks. If the computer does not list the phone at all, that is a different fault, and an iPhone not showing up in Finder or iTunes is the page for it.
A Level 10 member answering a stalled Finder backup added a step Apple does not mention. Go to Settings, General, Transfer or Reset iPhone, Reset, then Reset Location & Privacy. That clears every trust decision the phone has made and forces a fresh prompt.
4. Restart both machines, then retry once
Apple's third step. It belongs here rather than at the top.
Apple, same page: "Restart all your devices."
Restart the phone. Restart the computer. Plug in again, unlock, and try one backup. One clean attempt tells you more than five ragged ones.
5. On Windows, look hard at your security software
Apple names this explicitly, and only for PCs. That is why it sits at five rather than in a general list.
Apple, same page: "If you use a Mac, skip this step. If you use a Windows PC and iTunes won't respond or your backup never finishes, you might need to update, change, disable, or uninstall your security software."
A backup that never finishes is the exact wording. That matches what people describe when a security suite is quietly inspecting the connection.
Turn the protection off for one backup. Run it. Then turn it straight back on.
6. Clear disk space, and check the number Apple means
Narrower. It catches the failures that look random to you.
Apple, same page: "If a message says there's not enough disk space when you try to back up your device, free some space on your Mac or PC."
That warning does not always appear, though. A nearly full disk can throw a plain error instead. So check the computer's free space against the data on your phone before you conclude anything.
A Level 10 member advising an owner here told them to leave roughly ten percent of the phone's own storage free as well. Worth doing while you are there. Our page on an iPhone that says there is not enough storage to update covers how to make room quickly.
7. Delete the old backup, or move to a different machine
Last, because it throws away a copy you may still want. Apple offers a gentler alternative alongside it.
A part-written or corrupt previous backup can block a new one. In Finder, open the device, choose Manage Backups, then delete the failed backup and start fresh.
⛔ Do not delete your only good backup to fix a failing new one. Archive the most recent working copy first. Do that if there is any chance at all you will need it.
Apple, same page, offers the other way out: "If you own more than one computer, try to make a backup on your other Mac or PC. Or, use iCloud to back up your device and restore from your iCloud backup."
⚠️ And an honest ending. On the threads I read, two owners worked through every step above, including two calls to Apple Support in one case, and never got a computer backup to complete. If that is you, back up to iCloud and get your data safe first, then keep chasing the computer.
Status: iOS 26.6.1, checked 19 August 2026. Apple's steps are current. The USB hub fix is owner-confirmed once. Two owners on separate threads finished every step with the backup still failing.
Why does my iPhone backup fail on my Mac?
Most often the computer rather than the phone: an out-of-date macOS or Finder, a hub or dock between the two, a nearly full disk, or a corrupt earlier backup. Apple's own list starts with updating the computer and restarting everything.
What does "an error occurred while reading from or writing to the iPhone" mean?
It means the transfer broke partway rather than the phone refusing. Owners trace it to cables, hubs and ports more than to the handset. Apple's advice for the generic error is to check you are on the latest iOS.
Should I delete a failed backup?
Yes, a failed one is worth clearing. A part-written backup can block the next attempt. Never delete a good older backup to make room until you have a completed new one, or a copy somewhere else.
Is an iCloud backup as good as a computer backup?
For most people it covers the same ground, and it happens without you thinking about it. A computer backup can be encrypted to include saved passwords and health data. It also does not depend on your iCloud storage plan.
The Short Version
- Apple's page is a sequence, so retry the backup after each step.
- Update the computer first, because that fixes more cases than anything on the phone.
- Take the phone off any hub or dock and plug straight into the machine.
- Reset Location & Privacy forces a fresh Trust prompt when the old one is stuck.
- Apple names Windows security software specifically for backups that never finish.
- A nearly full disk can throw a plain error rather than a space warning.
- Two owners did everything here and still could not complete a computer backup.
Where to Next
Backing up is the one job where a silent failure costs you the most, and this one fails quietly. The bar moves, the bar stops, and no part of the screen tells you which link in the chain gave up.
Work down in order and you at least narrow it. Steps 1 to 4 cover the computer, the cable and the handshake, which is where most of it lives. Steps 5 to 7 are for the awkward cases.
If a hub turned out to be your problem, I would like to know which one, because that fix is reported by exactly one person and a second confirmation would let me move it up this page.
If your worry is that the backups you already made have vanished rather than that new ones fail, an iPhone saying No Backups Available is the page you want instead.
Isaac Smith is the founder and editor of PC Glance, a website that covers computers, laptops, and technology. He is a tech enthusiast and a computer geek who loves to share his insights and help his readers make smart choices when buying tech gadgets or laptops. He is always curious and updated about the latest tech trends.