best way to backup my iMac

Welcome to Apple Support Community.

To start a backup, you need an external hard drive. Here’s a few excellent ones sold by Apple: 

• LaCie Mobile Drive 4TB External Hard Drive USB-C - Apple
• LaCie 4TB Rugged USB-C Portable Hard Drive - Apple

If you have an iMac (Late 2015) or earlier, or a Mac mini (Late 2014) or earlier, you will also need this cable. 

You can then follow the steps in this Apple Support article to setup your Time Machine backup: Back up your Mac with Time Machine - Apple Support. 

Also, moving forward, I recommend that you use iCloud in addition to Time Machine to sync all your files and photos to all your Apple devices. Although iCloud is not a "true" backup service, iCloud can also act as an emergency off-site backup, but this is why iCloud should be used in addition to Time Machine. Here are some resources on setting up iCloud for Mac:

• Upgrade to iCloud+ - Apple Support
• Set up iCloud Drive - Apple Support
• Add your Desktop and Documents files to iCloud Drive - Apple Support
• Set up and use iCloud Photos - Apple Support

After you setup iCloud, turn off "Optimize Mac Storage" in System Preferences > Apple ID/iCloud. That way, all changes made to files in iCloud are also backed up to Time Machine. If you have this setting on due to a limited amount of storage on your Mac, that is fine. Just know changes won't be backed up to Time Machine, only iCloud.

Jack

I also use the Mercury Elite Pros for our iMacs. They use reliable 3.5-inch drives and have an independent power supply, something lacking in most "mobile" or "portable" drives that have to get all power from a USB port on the computer.

Portability is not really an issue for most iMac owners; reliability is. Over the last ~20 years I've never had a 3.5-inch drive fail, but had three 2.5-inch drives appear to simply wear out.

I buy the empty OWC enclosures and install SATA 6GB, 7200 RPM WD "Black" series drives. Very fast and no issues.

I have two of those on my "critical-needs" iMac. One does Time Machine backups and the other makes daily bootable clones with Carbon Copy Cloner (CCC). It was the CCC drive that saved 100% of my work when my old iMac died.

anne1954 wrote:

best way to back up my iMac

Back up your Mac with Time Machine - Apple Support

+ 1 to use Time Machine, you will need a high quality EHD to backup to. Personally, I have use the OWC Mercury Elite Pro's for over 15 years and they are still an excellent solution for a TM backup. You can find them by clicking OWC Mercury Elite Pro.

Best of luck.