I record a Photoshop action to save file as png format. It works except one thing: file sizes differ when I do manually save and when I play the save action (recorded exactly the same steps in manual save). For example, in manual save the file size is 10KB, in action save it becomes 40KB.

I tried several different files and got similar results. Action save always increases file size by around 20-30KB, which matters to me since I am doing iOS dev and keeping file sizes minimum is essential.

Any idea what cause the file size difference, and more importantly, how to get rid of it?

1 Answer 1


I found the problem: Mac Finder (and Adobe Bridge on Mac) don't update file size correctly.

Here is how I get to that conclusion. Firstly I use ImageOptim to reduce file size, and discover that size shown in ImageOptim is different from size shown in Finder. I thought Finder might needs a refresh. So I relaunch Finder, delete .DS_Store, yet nothing changes. Which size is correct?

As final resort, I copy files to my Windows laptop and check sizes over there. Truth be told: Windows size match ImageOptim size. Mac is wrong!

  • 1
    note that windows and mac report storage space differently: IIRC, mac reports storage as base-10 rather than base-2. What this means is that 1KB=1000 bytes rather than 1024bytes. It may also include the size of metadata or other OS-specific file information which is not actually contained within the file itself but is required by the OS for proper functioning.
    – horatio
    Mar 27, 2013 at 19:52
  • You get what you pay for when you buy these machines :) Mar 28, 2013 at 1:58

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