iPhoto and Photos Library duplication

Your Photos Library and the iPhoto Library are sharing the original image files and the previews using hard links.

So the image files, that need most of the storage are not duplicated, see these links:

• Photos saves disk space by sharing images with your iPhoto or Aperture libraries - Apple Support
• Six Colors: The (hard) link between Photos and iPhoto

You will not gain much storage by deleting the iPhoto Library.

Yes - as documented and posted here many times when you migrate photos are not copied but are hard linked to the Photos library - Photos saves disk space by sharing images with your iPhoto or Aperture libraries - Apple Support

And as you figured out though the finder reports each library as continuing the photos they do not - the photos that are hard linked exist only once for both programs to use

deleting either library will not affect the other - it only removes the hard links for that library - and it will return very little space for the same reason

You can delete either but it is not a good idea as restoring them if you want or need them can be difficult to impossible

LN

Suppose to? Not at all - you can delete either anytime you want -

deleting either library will not affect the other - it only removes the hard links for that library - and it will return very little space for the same reason

You can delete either but it is not a good idea as restoring them if you want or need them can be difficult to impossible

I would keep it until you are 125% sure you do not want or need it - but you can do anything you want and deleting it will not cause any problems until you want or need it - which may be never

LN