Moved Photos library to iCloud, but it's still taking hard drive space

I recently noticed that my Photos is taking a large amount of storage space on my hard drive. I enabled iCloud Photos, and the upload looks to be complete, but the size of the library has not decreased.

This library initially appeared on my Mac when I imported photos from my phone using a lighting cable as a way to back them up. The iCloud sync doesn't seem to have created duplicates, so I think it was able to detect that these are the same photos, but it's still taking a lot of space on my drive.

Is this expected? If not, what can I do to troubleshoot this?

In my preferences, Photos is set to "Optimize Mac storage".

Solution 1:

This is likely a combination of 2 things:

• Recent files … are always on your Mac.

• … optimised versions of your photos are always on your Mac.

https://support.apple.com/kb/guide/system-information/sysp4ee93ca4/mac

iCloud Photo Library always keeps low resolution thumbnails of your photos locally, and will also keep new, recently viewed or edited photos cached locally as space permits. The latter is purgeable by macOS when necessary, but only when necessary, so if you've turned on iCloud Photo Library from having all your photos locally, macOS doesn't go out of its way to clear that space unless it needs that space for something else.