How to Back Up an iPhone on Someone Else's Computer

Apple’s iPhone can be set up on a primary computer so that the phone is automatically synced to that computer’s iTunes program. You can, however, back up an iPhone on another computer as long as you know your passcode.

Passcode

Apple requires that you enter your passcode when attempting to connect your iPhone to a computer other than the one that it was initially set up with. This is done for security reasons to prevent unauthorized people from gaining access to your files. It is especially meant to deter thieves from wiping your phone and then reselling it.

If you have lost your passcode, you can't back up the iPhone on another computer, as the only way to remove the passcode is to reset the device using iTunes. Resetting erases all data and settings on your iPhone.

Back Up iPhone on Windows or Mac Computer

You can back up your iPhone on any Windows or Mac computer by following these steps:

1. Launch the iTunes program on your computer.
   
2. Plug your iPhone into the computer’s USB port with your iPhone sync cable. Wait for your computer to detect the device. If it does not then try a different USB port or cable.
   
3. Look at your iPhone and tap to “Trust This Computer” when prompted to. Selecting this setting allows iTunes to read your iPhone and access all data on it. You may also be prompted to enter your passcode.
   
4. Click your iPhone on the iTunes sidebar and then click “Summary.” Click the “Back Up Now” button.
   
5. Wait for iTunes to back up your iPhone. The back-up process may take anywhere from a few minutes to several hours depending on how much data is on your iPhone. Do not unplug the iPhone from your computer as this will restart the back-up process.
   
6. Check the iTunes summary for your phone and look for the “Latest Backups” section. You can check to see if your backup successfully completed as it will be listed here along with the time it was completed. You can unplug your iPhone safely at this point.
   

Restore iPhone Backup

After backing up your iPhone, you may want to restore the backup at some point. You can do this in iTunes by following these steps:

1. Launch the iTunes program and then plug your iPhone into the computer with your USB sync cable. Wait for your computer to detect the iPhone.
   
2. Click your iPhone on the sidebar in iTunes and then click “Summary.”
   
3. Click the “Restore Backup…” button. iTunes will check your iPhone’s current OS version and may prompt you to update your iPhone. Follow the on-screen prompts to do this.
   
4. Click the drop-down next to iPhone Name and select your backup.
   
5. Click the “Restore” button and wait for iTunes to restore your backup. Do not unplug your iPhone as this can corrupt your device if it is unplugged before the restore is complete. Note that you won’t be able to use your iPhone during the restore process.
   
6. Unplug your iPhone once iTunes tells you that the restore is complete.