Preview not opening all images in separate windows

I can reproduce this, sort of. Can you please confirm the threshold to see how reproducible it is? You state 'a dozen', perhaps you're approximating since I find the threshold to be 15 images. If I open 1-15 images, they open in separate windows. If I open ≥16 images, the first 14 open in separate windows and the remaining 2-n images open in a single window. For example, with 55 images, 14 in their own windows and the remaining 41 in a single window.

The limitation actually seems to be that Preview will not allow >15 open windows. If I open 15 images, the 16th images is added to an existing window.

There's a nuance there that also confirms it's not a memory limitation (I also have 48 GB so that seems really unlikely, especially since I can easily open 55 images in Photoshop), which is that if I move to a different Space then I can open an additional image in it's own window in Preview. If I have 15 images open in one Space, and open a new image in a different Space, subsequent images in that Space add to the first one and the same window. So really, for images in their own windows it's 15 images in one Space plus one additional image per additional Space. I typically use 5 Spaces so I can open 19 total images in their own windows, but if I add a 6th Space then I get an extra window.

Having said all that, this may be the expected behavior since it's not just with Tahoe...my Mac still on Sequoia behaves in exactly the same way.

Regardless of bug or feature, it's the way macOS is working and only Apple can alter that. To have Apple consider your feedback, submit it here:

Feedback - macOS - Apple

You're welcome. It does seem odd, I can easily have 20+ Safari windows open (and reportedly 500 tabs), but only 15 windows in Preview?

It's certainly manageable by macOS, I opened 15 images in separate windows in Preview (and I tried to push the system by opening RAW images that are 30-35 MB per image), and Preview is using only a small fraction of my system memory (which is at 18% pressure with no swaps). Heck, Apple's own forum isn't using much less memory. 😝

chocfruit wrote:

My workflow used to be: open all images, quickly close all the ones which I don't need/aren't good enough using cmd-W

FWIW, you can open as many images as you want in a single window then close one or more images that are selected in the sidebar using Command-Shift-W.

As noted, 15 images appears to be the limit for Preview set by Apple. Personally I have no idea why anyone would want to open 15 separate images at one time, much less more than that.

chocfruit wrote:

Preview - open all files in own windows, Tahoe 26.1

In System Settings I have "prefer tabs when opening documents" set to "never". In Preview I have "open each file in its own window" selected.

Yet when opening 30+ images via selecting in Finder and using "open with Preview" only a dozen are opened in separate windows, with the rest in one tabbed window.

How can I stop this? It is absolutely infuriating.

You stop it by not doing it.

For one— opening 30 Preview windows seems unmanageable by any account. (?)

I would suggest you create a more realistic work flow whatever you are doing or trying to accomplish....

If you think this is an issue— present it to Apple Product Feedback - Apple

My guess is Apple is not going to change Preview for the very few people that may want to open more than 15 separate windows at a time. In 15 years on ASC, yours is the first post I've seen that had such a need. In any case, you can use alternative apps if needed.

It might depend on how much available RAM you have to work with.

Not sure what is going. It could be a bug in Preview.

You might want to look at opening the image as a Contact Sheet.

Just out of curiosity how big are these images? Dimensions and MB's Size?