How to back up Photos

Or, do what I do and periodically just drag the Photos library to the external drive.

I usually keep the last two libraries on the external.

In addition, I use time machine to back up my photo library, too.

My photos are too precious to trust it to one backup.

That will depend on whether you have iCloud Photos enabled or not. If you are syncing your Photos Library with iCloud Photos between your devices, it will not suffice to run Time Machine or or make a copy of your Photos Library, because the Photos Library may be incomplete, even with the Photos > Settings > iCloud > Download Originals" enabled. The Photos.app does not have a reliable indicator, if all originals have been downloaded from iCloud. In addition to making a copy of the Photos Library you need to save the original image files as well by exporting hem from photos with "File > Export > Export unmodified Original".

You can do what I do and that is use Carbon Copy Cloner to close and make incremental backups of my main library to a cloned library on an external drive.

It's very fast because it only copies those new or modified (edited Photos) files to the backup library and deletes those photos from the backup library that were deleted from the main library. You can have CCC backup hourly, daily, on a specified schedule. I use daily.

Then you can have Time Machine backup both your boot drive and the external drive for a second backup.

Of the ones Matti mentioned, Time Machine if free and comes with the Mac System, at

System Settings>General>Time Machine

Time Machine will make incremental backups every hour (or however you set it.) These backups are fast and unobtrusive, because they only record what's changed since the last backup. There aren't a lot of settings to mess with; it just works.

Back up your Mac with Time Machine - Apple Support

The other apps that Matti referenced will do pretty much the same thing, but they have more options and do more stuff. I didn't see them on the App Store, but they are nonetheless trusted by experts.

How to back up Photos to an external drive:

Time Machine or some 3rd party app like Carbon Copy Cloner (my long-time favorite) or Super Duper.

léonie wrote: … I am sticking with Apple Photos just because of iCloud Photos syncing

I agree-- iCloud painlessly keeps my Mac, phone, and iPad synchronized-- something that I use to have fits with. And I like the general organization tools. Lots could be better, but that looks to be true with everything. I also think that I like that the originals are locked down, away from the general population of files. Of course I keep backups, but over the years they have gotten themselves lost to hard drives all over the place, mixed in with other files.

I also like the editor. I've been using Lightroom, and I've recently been experimenting with Photometor, but when I get pictures back to Photos, I always seem to have just one more small tweak to add that makes a big difference in the image.

léonie wrote:

The Photos.app does not have a reliable indicator, if all originals have been downloaded from iCloud.

It may not be reliable, but at least these days Photos does sometimes have an indicator that it is "Downloading nnn Originals" (or waiting to do so). I ran into those status messages at the tail end of downloading large Photos libraries from iCloud recently on multiple Macs and system levels (at least Sequoia and Tahoe).

I don't use iCloud Photos. There is no reason to share the image of what pickles I am supposed to buy with my Mac at home.

I have used Super Duper, but it seems to be getting less and less useful.

I am sticking with Apple Photos just because of iCloud Photos syncing and the ease of Hand-off. My Photos Library is identical on all my Macs, and also on my iPhone, iPad, Vision Pro. All edits are lossless, I can revert them easily and independently. I can work with my photos whatever device I am having with me, when I have time to spare to weed out the photos library or tag the photos.