PSB file size increasing by 16-fold when saved with latest version. Why?

[Glacier David]

I just edited a 8 GB psb file in Photoshop version 24.0.1 that hadn't been touched since last March 2022. The edits were minor changes to text. When I resaved, the new file was 128 GB, a whopping 16-fold increase. Yikes! Neither the old nor the new file were compressed (and when the new file is compressed, it is only 4 GB). I'm using Windows 10 Pro.

I get the same kind of behavior with another 3 GB PSB file which had not been edited since last May. It increases to a 6 GB file with a small text edit (a 2-fold increase).

Is this massive increase in PSB file size a bug in the latest version of Photoshop? Or has some setting changed in an update that I need to reset? Or other...?

Thanks,

David

[D Fosse]

There was a bug in recent versions, now fixed, that applied RLE compression to PSD/PSB even when all compression was turned off in Preferences. So that can explain a small difference (it will be bigger now in the latest version).

But 16 x bigger sounds crazy. The only thing I can think of that can explain that is that you have inadvertently added some content outside the visible canvas boundary.

Try Image > Reveal All.

[Glacier David]

Good thought but unfortunately, Reveal All did not reveal any hidden content outside the visible canvas. However, there are 28 linked psd files within this PSB; but their total size is 13.5 GB. Even if included, that's not enough to go from 8 to 128 GB.

I've attached an image of the file folder that shows the file sizes for (1) original PSB at 8 GB, (2) recently saved PSB at 128 GB, and (3) the recently saved compressed PSB at 4 GB.

[craigs51993353]

Hi David - I don't know if you're still having the problem or not but I have been frustrated by the same thing. What I experienced was trying to save a 400mp old psd file after adding a single curves adjustment layer and Photoshop 2025 changed the 400mb file to a 2.4gb file requiring saving as psb file. What I found was that if I did the edit in Photoshop 2021 adding the curves layer added essentially nothing to file size and I was able to save the file as a psd, no problem.  What appears to be happening is that files originally edited on legacy versions of Photoshop jump tremendously in size when saving on more current versions (perhaps Photoshop somehow replicates the file in each succeeding version before saving in the current version?? Who knows). Try saving your file in an older version of Photoshop and see if that solves your problem, it worked for me. 

Craig

[paulewilliams]

I am also getting file increases also in photoshop 2025 on PSB files made in photoshop CS6 , the files are  saving with about a 100% file size increase, can't imagine why as bit settings etc remain the same. I expected the file sizes to go down as I collapsed layers but the oposite happened. A real nuisance when you are uipdating archive drives with final versions that have little space left. 

[paulewilliams]

Actually I think I have worked out why the file sizes increase. I have no idea now if I had the compress PSD/PSB files turned on or off in CS6. I have it turned off in CS 2025 so I suspect the older files I am openeing now were possibly compressed in the CS6 so when I re-save them that are going to be bigger. Thats my hunch anyway. 

[D Fosse]

If it's about a 2x increase that's the likely explanation. Compression has always been on by default, in all versions.