Photoshop: Why are .PSD's so much larger than .JPG's?

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  • Updated 6 years ago
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Why are .PSD files so much larger than .JPG's?
Even if these .PSD's consist solely out of JPG's?


I have a 500kb JPG file.
When saved as a .PSD it gets double the size. 1 Mb.

But what's more: when it's made into a layer, and then saved as a .PSD
It turns 2 Mb!

That's 4 times the size, for the exact same pixel count and quality.
A 1 layer .PSD is 4 times the size of the exact same layer made into a .JPG.
Something tells me that isn't very efficient.

With this small example, it's obviously not that annoying.
But sometimes I'm working with 1 Gb .PSD's, of which I now think can be way smaller...

Is there a reason for this?
Photo of Joost de Haas

Joost de Haas

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Posted 6 years ago

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Photo of Jeffrey Tranberry

Jeffrey Tranberry, Sr. Product Manager, Digital Imaging

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Official Response
Yes. PSDs are uncompressed files and JPEGs are compressed. If you add a layer, it will double in size because you have double the # of pixels.