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I've recently learned that hiding Photoshop layers will reduce the file size.

After searching around the Adobe forums I can't find anything stating this. There are only about half a dozen sites on Google that I found mentioning this trick as well.

I have a 300mb file with roughly 6 layers. When the layers are hidden it trims about 100mb off of the total file size.

I'm wondering what information is either compressed or lost by hiding layers? Will the file still be safe for print? Will the file still maintain it's compatibility options for other programs like Lightroom?

All of the articles I found talking about this trick don't explain exactly what's going on with this, and what information is being left out or compressed. Any ideas would be appreciated. Thanks!

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  • Compressing (zip/rar) your PSDs can also help reduce the file size.
    – Krazer
    Apr 6, 2013 at 20:02
  • I'm not specifically looking to reduce the file size, but curious as to what information is being removed when hiding layers.
    – Aaron
    Apr 6, 2013 at 23:31

3 Answers 3

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I just did the test and in fact in my test with all layers hidden got a file about 1 MB smaller.

I proceeded to save it with all layers visibility on but this time disabling the "maximize compatibility" option - the result was the same.

So the thing is, Photoshop saves some kind of high res preview of the file when "maximize compatibility" option is turned on. This info is then used in programs like irfanView, google viewer and even adobe bridge for previewing purposes. With all layers visibility hidden this preview will be essentially empty thus the file size decrease.

You can turn off maximize compatibility in preferences > file handling

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  • Maximize compatibility has to remain on. I was thinking it was the previews, but seeing a 100mb drop for 6 hidden layers seems to me like some other information is being dropped out. Adobe doesn't even acknowledge this trick on their site, and the places that do don't say what's being compromised for the file size reduction.
    – Aaron
    Apr 6, 2013 at 17:56
  • with layers hidden the preview will be empty. Just try to save your file with maximize compatibility turned off but with all layers visible and you should expect similar results
    – Patareco
    Apr 6, 2013 at 18:01
  • I still think additional data is dropping out or being compressed. How could the previews take up 1/3 of the file size?
    – Aaron
    Apr 6, 2013 at 18:08
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    So, I've worked with a mock file some more. 1 File with 3 layers (photo, smart object, adjustment layer) - in a group. Visible=20mb, hidden=13mb. How can preview images take up that much space? A full quality jpg of the image is 1.3mb - leaving a huge difference. Also, changing the preferences to not save preview images arrives at a different file size. So, what exactly is getting dropped out/compressed/compromised?
    – Aaron
    Apr 6, 2013 at 18:46
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I suspect it would take someone from the Photoshop Dev team to really explain this clearly.

My understanding is that internal proprietary data regarding visible layers is either included or not based on layer visibility state. This is combined with the internal composite preview to further alter file size.

For example, if a layer is not visible, Photoshop does not need to store the data generated when the layer is visible. Things like anti-aliasing, blend modes, opacity variations, etc. (essentially blending options) are all superfluous when a layer is not visible. So that data does not need to be stored and can quickly be regenerated when the layer is made visible at a later point. Blending options data can get lengthy because each layer can interact with every layer below or above itself.

The short answer... Composite data is stored differently.

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  • Thanks. Just to clarify, I'm dealing with a situation where the file needs to have the highest compatibility possible since it will be distributed to many different users on different platforms and versions. In this case, would you consider hiding layers to be a safe option? Thanks!
    – Aaron
    May 7, 2013 at 1:05
  • Yes. With maximize compatibility checked in the prefs, I've never had any issues moving .psd files between app versions, other than obvious feature-centric implications.
    – Scott
    May 7, 2013 at 1:22
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A file preview is not the same as a flattened, full res snapshot of your image. The latter is saved for compatibility purposes, when you save it as such. The layers are flattened but there should be no other form of compression in the compatibility version of the file, hence the large size.

If you don't need to worry about compatibility, which you obviously don't if you're turning the layers off, then just turn off compatibility mode. It's usually inactive on my files. If you have to distribute a file for another person's use, just save a version.

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