How to do it
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Open the iCloud Photos settings
Go to Settings, tap your name, tap iCloud, then tap Photos. Turn on Sync this iPhone.
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Choose Optimize iPhone Storage
In iOS 27 or later, tap iPhone Storage, then make sure Optimize iPhone Storage is selected. In iOS 26 or earlier, you choose Optimize iPhone Storage directly.
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Check you have enough iCloud space
Optimize works as long as iCloud has room for your full library. Go to Settings, tap your name, tap iCloud, and look at how much space is left.
What does Optimize iPhone Storage change?
By default, photos and videos are stored on your iPhone in their original, high-resolution version. With iCloud Photos, Optimize Storage is on by default, so your iPhone can keep less while you still reach the full-resolution collection (Apple). Your iPhone starts with the photos and videos you access least when it needs more room (Apple).
Why did deleting 1,000 photos free so little?
Vendor guides such as Lumina Clean note that with an optimized library, deleting only removes the small local version. Apple adds that deleting a photo with iCloud Photos on removes it from all your other devices too (Apple). So deleting is a way to remove photos, not a way to shrink the library.
What changed in iOS 27?
In iOS 27 or later, you tap iPhone Storage first, then choose Optimize iPhone Storage (Apple). Earlier versions go straight to Optimize iPhone Storage.
Where can PicWay help?
Space only frees up once you delete the original, and iOS doesn’t let an app empty Recently Deleted for you, so that last step happens in the Photos app.
Does Optimize Storage delete my originals?
No. Full-resolution photos and videos stay in iCloud as long as you have enough iCloud space (Apple). Keep a backup of anything important anyway, because iCloud Photos isn’t a backup (Apple says photos aren’t duplicated in your iCloud backup).