Why is my photo library bigger on my hard drive than in iCloud?
My Photo Library is near 140GB instead on iCloud I have near 105GB of photos? Why?
MacBook Air (2018 or later)
iCloud is storing the original image files, but your Mac is storing additional working copies for browsing your photos. There are also previews for the media Browser.
When I look at my Photos Libraries, the additional working copies need roughly 15% of the size of the library in iCloud.