Q: Can I delete my iPhoto library after I migrated it to Photos library?

Yes

But it is not recommended - you may want or need it in the future and if you delete it that can be a problem

And usually there is no reason to delete it quickly as it will not save very much disk space at all Photos saves disk space by sharing images with your iPhoto or Aperture libraries - Apple Support

LN

Yes, but I would hang onto it for a while until Photos becomes a more accomplished replacement. Your iPhoto application is still in your Applications folder, so you may want to hang onto it, as well. If the version you have won't open, then see the following:

Terence Devlin

Apr 14, 2015 2:21 PM

Re: Is Iphoto gone ? i want it back!

Go to the App Store and check out the Purchases List. If iPhoto is there then it will be v9.6.1

If it is there, then drag your existing iPhoto app (not the library, just the app) to the trash

Install the App from the App Store.

Sometimes iPhoto is not visible on the Purchases List. it may be hidden. See this article for details on how to unhide it.

http://support.apple.com/kb/HT4928

One question often asked: Will I lose my Photos if I reinstall?

iPhoto the application and the iPhoto Library are two different parts of the iPhoto programme. So, reinstalling the app should not affect the Library. BUT you should always have a back up before doing this kind of work. Always.

I opened my IPhoto library with the Photos app. Can I safely delete that IPhoto library now?

Wait until you have checked if each and every photo migrated well. You may only notice later if individual photos are missing to corrupted. At least keep a backup copy of the iPhoto Library on an external drive.  Some library coppruptions in your new Photos library can be more easily fixed by migrating the previous iPhoto Library again after repairing it in iPhoto.