The short answer
Both settings keep full-resolution originals in iCloud. The difference is what stays on the phone. Download and Keep Originals stores a full-size copy of every photo on the device. Optimize iPhone Storage keeps smaller device-sized versions and fetches the original on demand, which can save tens of gigabytes. Neither setting reduces image quality permanently, and neither is a backup.
You will find the choice at Settings → Apps → Photos, under iCloud Photos. It appears only when iCloud Photos is switched on. The two options are worded confusingly enough that plenty of people pick the wrong one, so here is what each actually does.
What Optimize iPhone Storage does
Your full-resolution originals are uploaded to iCloud. Your iPhone then keeps a smaller version of each one, sized for the device's screen, and frees the difference.
When you open a photo, zoom into it, edit it, or share it, iOS downloads the original in the background. On a good connection this is quick enough that you may never notice. On a poor connection, or offline, you get the smaller version — which is where the complaints about "blurry photos" come from.
Crucially, iOS only swaps files out when it needs the space. On a phone with plenty of room free, Optimize mode may keep almost everything at full resolution and look identical to the other setting. It is a pressure valve, not a permanent compression.
- Saves: potentially tens of gigabytes on a large library
- Costs: a download delay when opening older photos, and reduced quality when offline
- Best for: 64 GB and 128 GB phones, and anyone with a library larger than about a third of their storage
What Download and Keep Originals does
Every photo and video exists at full resolution in two places: iCloud and your phone. Nothing is ever swapped out, nothing is ever fetched on demand, and everything works identically offline.
The cost is simply that your entire library has to fit on the device. A 180 GB library does not fit on a 128 GB iPhone, and iOS will tell you so.
- Saves: nothing — this is the expensive option by design
- Costs: your library's full size in device storage
- Best for: 512 GB and 1 TB phones, photographers who edit on device, and anyone frequently offline or on poor connectivity
Side by side
| Optimize iPhone Storage | Download and Keep Originals | |
|---|---|---|
| Originals stored in iCloud | Yes | Yes |
| Full-resolution copy on device | Only when there is room | Always |
| Device space used | As little as a few GB | Your library's full size |
| Opening an old photo offline | May show a smaller version | Always full quality |
| Editing an old photo | Downloads the original first | Immediate |
| Quality permanently lost | No | No |
| Counts against iCloud quota | Yes, in full | Yes, in full |
| Is it a backup? | No | No |
The quality question, answered properly
The most common worry about Optimize mode is that it permanently degrades your photos. It does not. The original file is intact in iCloud, and switching to Download and Keep Originals pulls every full-resolution file back down.
What is true is that the *version on your phone at a given moment* may be lower resolution, and that has real consequences:
- AirDropping an old photo offline may send the smaller version.
- Printing from the phone without waiting for the download can produce a soft print.
- Third-party apps reading your library may receive the optimised version if the original has not been fetched — relevant for editors and print services.
- Exporting your whole library requires every original to download first, which on a large library takes hours and a lot of bandwidth.
Why neither one is a backup
iCloud Photos is a sync service, not a backup service, and the distinction matters more than almost anything else on this page.
Sync means changes propagate. Apple is explicit: *"If you use iCloud Photos, and delete photos and videos from one device, the photos and videos will be deleted on your other devices."* Delete a photo on your iPhone and it leaves your iPad, your Mac, and iCloud.com. Empty Recently Deleted and it is gone everywhere, permanently.
A backup is a separate copy that does not change when the original changes. If losing your photo library would be a disaster, you want at least one of:
- A periodic export to a computer or external drive (Finder, Image Capture, or Photos on a Mac).
- A second cloud service with its own copy — Google Photos, Amazon Photos, Dropbox — that is not syncing deletions from Apple's library.
- Both, if the library is irreplaceable.
Which one should you choose?
- 01
Check your library size
Settings → General → iPhone Storage → Photos gives the current device figure. For the true library size, look at Settings → [your name] → iCloud → Manage Account Storage → Photos.
- 02
Compare it to your device capacity
If your library is more than about a third of your total storage, Optimize is the sensible default. Below that, either works and Download and Keep Originals is more predictable.
- 03
Weigh how often you are offline
Frequent flying, patchy signal, or travel without data pushes you towards keeping originals — assuming they fit.
- 04
Switch, then let it settle
Changing to Download and Keep Originals starts a potentially large download; changing to Optimize frees space gradually as iOS needs it, not instantly. Neither is immediate, and neither loses anything.
Common questions
Does Optimize iPhone Storage reduce photo quality?
Not permanently. Full-resolution originals stay in iCloud, and the phone keeps smaller versions only when it needs the space. Opening, editing or sharing a photo downloads the original. Switching back to Download and Keep Originals restores every full-size file to the device.
Where are my original photos if Optimize iPhone Storage is on?
In iCloud. You can see them at full resolution on iCloud.com, on any other device set to keep originals, or by switching your iPhone to Download and Keep Originals and waiting for the download to complete.
Does Optimize iPhone Storage save iCloud space?
No. It only affects device storage. Both settings upload every original to iCloud and use exactly the same amount of iCloud quota. To reduce iCloud usage you have to delete photos or upgrade the plan.
Can I use Optimize iPhone Storage without an iCloud subscription?
Only if your entire library fits in the free 5 GB, which for most people it does not. The setting requires iCloud Photos to be switched on, and iCloud Photos requires enough quota to hold your whole library. Without it, photos stop uploading and the feature cannot work.
Is iCloud Photos a backup of my photos?
No. It is a sync service. Deleting a photo on one device deletes it everywhere, and permanently deleting it from Recently Deleted removes it from iCloud too. For a real backup you need a separate copy that does not mirror deletions — an export to a computer or drive, or a second cloud service.
Why do my old photos look blurry for a second before loading?
That is Optimize mode working as designed. The phone displays its smaller local version while fetching the full-resolution original from iCloud. On a slow or absent connection the placeholder is all you get until connectivity returns.