Reduce Photoshop file size

For a recent paper that we wrote, I assembled several figures in Photoshop. After finishing all the figures, I wanted to share them with my co-authors on Dropbox, only to realize that the total file size was 1.4GB. 1.4 Gigabyte of data for 12 figures! Fortunately I have 1TB of storage space through Dropbox Pro, so that shouldn't matter.

However, I remembered seeing a Tweet about that you can reduce the file size of a Photoshop file by adding solid white as the topmost layer.
So I thought I'd give it a go, and it worked! I managed to reduce the file size of my files from over 1.4GB to 984MB simply by adding a layer of solid white to the files!

Here are the steps to reducing the size of a Photoshop file:

  1. Add a new layer as the topmost layer.
  2. Fill the layer with solid white.
  3. Save.

The downside of it is though, that my co-authors will now see a blank file as soon as the open the file...

Why this works? I think to remember that it had something to do with how Photoshop creates thumbnails for the files. I would have loved to credit the original source, unfortunately I cannot find the Tweet anymore. However if you search for "Photoshop file size" you find many more resources about this. For example this blog post contains even more tricks.

Here are some example file size reduction I managed to achieve through that easy trick:

  • 219MB → 158MB
  • 7.18MB → 5.53MB
  • 256MB → 228MB
  • 100MB → 71MB