how to back up iPhone to iMac

1. Connect iPhone and your computer with a cable.
2. In the Finder sidebar on your Mac, select your iPhone.
3. To use the Finder to back up iPhone, macOS 10.15 or later is required. With earlier versions of macOS, use iTunes to back up iPhone.
4. At the top of the Finder window, click General.
5. Select “Back up all of the data on your iPhone to this Mac.”
6. To encrypt your backup data and protect it with a password, select “Encrypt local backup.”
7. Click Back Up Now.

Note: You can also connect iPhone to your computer wirelessly if you set up syncing over Wi-Fi.

Back up iPhone - Apple Support

This link explains how to backup an iPhone to a Mac --> How to back up your iPhone, iPad, and iPod touch with your Mac - Apple Support

You can save a backup of your iPhone to your Mac. Newer OS / Macs do this via the Finder, while older ones still use iTunes. See this Apple Support document and scroll down to the Mac section.

Back up iPhone - Apple Support

NoWoodSmoke wrote:

how to back up iPhone to iMac

Links to Mac and PC backups: How to back up your iPhone, iPad, and iPod touch - Apple Support

As you have likely already encountered that article and are having trouble getting the Mac or PC to recognize the device, follow the instructions in the Related Article, linked above, to get your computer to recognize your device, including updating the iPhone and the Mac or PC to current.

More generally… If there are any add-on anti-malware apps, add-on cleaner apps, add-on VPN apps, or similar, remove all that, restart, and try again.

Important note, maybe.........If you opted to encrypt the backup, it might be a good idea to write down that password and keep it in a safe place. You won't be able to access the backup later if you cannot remember the password.