I've made a big mess in Photos - please help!

Thanks very much, Tony. Appreciate the thoughts here. I think given my issues and the desire to free space up generally on my Mac, it's probably time to move my library to an external drive. One of the reasons I had hesitated to do so was not having everything backed up to iCloud, but it's a relief that I can continue to use iCloud with the external drive.

Here's my last question, then: because my current Photos Library is going through this re-sync process and it will likely take days/weeks given the size, by moving now to an external drive won't that problem just continue? In other words, right now Photos is stuck at updating 609 photos, and my entire library seems to be duplicated in the "Unable to Upload" folder within Photos. If I move everything to that external drive, isn't the problem just going to be replicated on the external drive? Or is what you're saying that it will be replicated, but rather than going through the re-sync on the Mac it will just go through the re-sync on the external drive?

Thank you, Leonie. I'm a bit confused though. If I delete the "Unable to Upload" album, that will effectively delete all of the photos in my library (I've done a couple of tests by deleting photos from the album, which deletes them from the library). So is what you're saying is to export just the "Unable to Upload" album to an external drive, then delete them (and effectively clear out the entire library), and then reimport them?

That seems potentially doable (though having to use an application to convert items with another application seems a bit daunting, but I'll put that aside for now), but how does this work with the fact that I have all of these in iCloud? My Photos library is currently optimized for storage purposes, with full res versions in iCloud. If I export the optimized "Unable to Upload" album, and then reimport, isn't that going to effectively layer over optimized versions of photos on the full res versions in iCloud?

Ooh, Tony that is indeed a much much simpler strategy! I like the sound of simple for sure! I'm fairly confident that most, if not all, of the pictures and videos that I need are in iCloud, and as you say I should be able to export anything from current library that's not in there and then reimport into the new library.

If I embark on this journey, by pointing the new system library on the external storage does the sync go from iCloud to the Photos library? I always thought the sync was the other way, i.e., any photos in the Photos library get synched to iCloud, but it sounds like what you're saying is that it works both ways?

Also, how does it work with the whole "Download Originals to this Mac" vs. "Optimize Storage" when it comes to having the Photos library on external storage? Same as it would work as if the external storage drive was the Mac?

Thanks for all your continued help on helping me solve this issue!

Really, really helpful stuff here Tony. Thank you so much. If you are so inclined, any recommendations/suggestions on what external to go with in terms of size and SSD/HDD for purposes of Photos? Re size, seems like I could purchase a 4TB drive but if my backup is only 2TB in iCloud, not sure that's completely helpful. Re SSD/HDD, would there be a noticeable difference in working with an HDD as the drive? Hate to bug you one more time but you may have some thoughts on this so thought I'd ask!

Tony - me again! So, went through the above steps, worked like a charm. All photos and videos are now on the external hard drive.

Just one problem: my Mac is still showing 275GB of storage in Photos (by going to About This Mac>Storage> and then clicking “Manage”). Now, I do have some iMovie and other movie files that are large, but those are contained in the “Documents” list after clicking Manage, while “Photos” is showing 275GB. Obviously I’d love to free up all that storage for updates, speed, etc., but....I don’t even know where that 275GB is coming from. Any ideas?

Thanks, Tony. I downloaded Disk Inventory X, which shows me I have even less space than About This Mac says I have haha.

The good news is, this does give me a good sense as to where all the storage space is going. One item I’m stumped on though is the following in a Movies folder: a .QT file with a long string of characters after (full file name is .QT-0a76-cf92ab02-bfffe2b8-00). But there’s no way to actually view the file to see what it is, and I can’t seem to find where it is in Finder even after telling Disk Inventory X to reveal in Finder. I’m ok with deleting it unless it’s a system file that will cause bigger problems. But the file is 19.6GB, so would love to free up that space if it’s not necessary. Any thoughts as to whether it’s safe to do so?