How to backup data before adding memory
Is it imperative to do a backup when adding memory to your computer
[Re-Titled by Moderator]
Mac Pro, macOS 12.7
What you should be striving for is a backup that is ALWAYS up-to-date, so that events like memory upgrades are not things that you need to fear.
If you do not have a recent local, disk-based backup, your computer is like a ticking Time bomb. You are only one disk failure, one crazy software, or one "oops" away from losing EVERYTHING! Drives do not last forever. It is not a question of IF it will fail, only WHEN it will fail. In addition, you never know when crazy software or Pilot Error throws away far more than you intended.
If you are using another direct-to-disk backup method that you prefer, and you currently have a recent disk-based backup, that is great. If not, you should consider using Built-in Time Machine. Take steps to acquire an external drive as soon as possible. If you buy one, a drive 2 to 3 times or larger than your boot drive is preferable for long term trouble-free operation. Do not pay extra for a drive that is fast. (You can get by for a while with a "found" smaller drive if necessary, but it will eventually become annoying).
Attach your external drive and use
System preferences > Time machine ...
... to turn on Time Machine and specify what drive to store your Backups on. It may ask to initialize the new drive, and that is as expected. APFS format is default format if running MacOS 11 Big Sur or later.
Time machine works quietly and automatically in the background, without interrupting your regular work, and only saves the incremental changes (after the first full backup). Time machine backs up your machine — including every connected drive that is in a Mac compatible format. it can not back up Windows format drives.
Time Machine's "claim to fame" is that it is the backup that gets done. It does not ruin performance of the rest of the computer while doing its backup operations. You do not have to set aside a "Special Time" when you only do backups. When you need it, your Time machine Backup is much more likely to be there.
How to use Time Machine to Backup or Restore your Mac:
Back up your Mac with Time Machine - Apple Support
