what is icloud photo and what happens if I clear it

iCloud isn't actually a true backup service. It is a syncing service. When you delete a photo from iCloud, the photo will delete everywhere simultaneously. This link will better explain how iCloud Photo works.

If you are out of space and if photos are taking up the most space, connect your iPhone to your computer (Windows or Mac) and upload the photos to your computer. Then you can remove the photos from iCloud to free up space, but the photos will no longer be accessible on your iPhone unless you choose them to put back via a sync from your computer to your iPhone.

This link explains how to upload photos to your computer, from your iPhone --> Transfer photos and videos from your iPhone or iPad to your Mac or PC - Apple Support

Shaniaclss Said:

"what is icloud photo and what happens if I clear it: I'm trying to free up storage so I can back up my phone. But my phone storage is too high even after clearing it> So I wanted to try and clear my iCloud storage, but I was curious what happens if I did."

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Safely Clearing iCloud Storage:

One unique method...

Download All of iCloud:

One thought would be to download all of iCloud, and then search through it in Finder on a Mac. You would download it to an external drive, and then open the drive in Finder. Search through it using the search bar on the top-right corner of the Finder window. Once found, you can trash what's iCloud using Finder. Use my user tip: Getting a Quick and Direct "iCloud Drive-to-External Hard Drive" Download - User Tip