When the Photos library is the biggest thing on your iPhone, the Optimize iPhone Storage setting is the fix built into iOS. It keeps the full-size originals of your photos and videos in iCloud and leaves smaller, space-saving versions on the phone, downloading the full file when you open it. To switch it on, go to Settings > [your name] > iCloud > Photos, turn on syncing, and choose the Optimize option. It does need enough iCloud storage to hold the whole library.
Burst sequences can hold many near-identical frames, so it can also help to clean up burst photos on iPhone.
What Optimize iPhone Storage actually does
Optimize iPhone Storage only works together with iCloud Photos, Apple’s service that keeps one photo library in sync across every device signed in to the same Apple Account. Once iCloud Photos is on, your iPhone has two ways to store that library:
- Optimize iPhone Storage: iCloud holds the original, full-resolution version of every photo and video. The iPhone keeps space-saving versions instead, and when the phone starts running low on space, iOS optimizes the library starting with the items you open least.
- Keeping the originals on the iPhone: every photo and video stays on the phone at full size, and iCloud holds a synced copy too. This saves no space on the iPhone at all.
Apple notes that when you use iCloud Photos, Optimize Storage is on by default. So if you already turned on iCloud Photos at some point and your phone is still full, the setting may already be doing its job and the space is going somewhere else (apps, messages or downloaded media). The section on checking your storage below shows how to tell.
Two points are easy to miss. First, nothing is deleted from your library: every photo is still visible in the Photos app, still searchable, and still in iCloud at full quality. Second, the savings are not instant. iOS does not shrink the whole library the moment you flip the switch; it frees space gradually as the phone needs it, and only after the originals have finished uploading.
Turn on iCloud Photos and Optimize iPhone Storage
These steps are for current versions of iOS. Apple’s own support pages use two slightly different sets of labels for the same switches, so your screen may say either version; both are noted in the steps.
- Open the Settings app.
Older iOS version shown; current screens look different. - Tap your name at the top of Settings, then tap iCloud.
- Tap Photos. On some versions it is listed in a section called Saved to iCloud.
Older iOS version shown, where photo settings were under Photos & Camera; current versions put them under your name > iCloud > Photos. - Turn on Sync this iPhone (Apple also labels it Sync this device). This is the iCloud Photos switch. Your library starts uploading to iCloud in the background.
- Choose the Optimize option:
- In iOS 27 or later, tap iPhone Storage, then make sure Optimize iPhone Storage (or Optimize Storage) is selected.
- In iOS 26 or earlier, there is no extra screen: choose Optimize iPhone Storage directly on the Photos screen.
Older iOS version shown, where the switch was called iCloud Photo Library; current versions call it Sync this iPhone.
A check mark next to the Optimize option means it is active. There is nothing else to save or confirm.
If you can’t find the setting
- No name at the top of Settings: you are not signed in to an Apple Account on this iPhone. Tap the sign-in prompt at the top of Settings first, because iCloud Photos needs an account.
- Photos is missing from the iCloud screen: scroll through the full list of apps that use iCloud on that screen, and if the switch is dimmed, check whether Screen Time restrictions or a school or work profile manages the device.
- Older iOS versions: photo storage options used to sit in Settings > Photos (and, much earlier, Settings > Photos & Camera), and the switch was called iCloud Photo Library. If your phone runs an older release, look there.
Make sure iCloud has room for the whole library
Optimize can only send originals to iCloud if iCloud has space for them. Every Apple Account comes with 5 GB of free iCloud storage, and that 5 GB is shared with iCloud Backup, iCloud Drive, Messages and Mail, according to Apple’s page on managing iCloud storage. Most photo libraries are bigger than that, so the setting often needs an iCloud+ plan, Apple’s paid storage upgrade.
To see how much iCloud space you have and what is using it, go to Settings > [your name] > iCloud and look at the storage bar at the top. The steps to see what is using your iCloud storage from an iPhone walk through that screen in more detail.
A quick way to size things up: compare the space Photos uses on the phone (from Settings > General > iPhone Storage) with the free space left in iCloud. If the library is 40 GB and iCloud has 4 GB free, the upload will stall and iOS will warn that iCloud storage is full. If you are unsure how the two kinds of storage relate, it helps to read about the difference between device storage and iCloud storage before paying for anything, because buying iCloud space does not add space to the iPhone itself.
One more consideration Apple points out: iCloud Photos is a sync service, not a separate backup. Your iCloud Backup does not duplicate a library that is already in iCloud Photos, and a photo you delete on one device is deleted everywhere. If the pictures matter, keep an extra copy somewhere else, such as on a computer.
Give the first upload time to finish
Turning on iCloud Photos starts a full upload of your library, and the phone cannot replace any original with a smaller version until that original is safely in iCloud. Apple says the time it takes depends on the size of your collection and your internet speed, and large libraries take longer.
To help it along:
- Stay on Wi-Fi and keep the iPhone connected to power, especially overnight for a large library.
- Open the Photos app now and then to see the upload status it shows; in iOS 26 or later the sync controls sit behind the profile button in Collections.
- If the upload is slowing down something else, current versions let you pause it for a day. In iOS 26 or later, open Photos, tap Collections, tap the profile button, then tap Pause. Apple notes that the option may not be available depending on the library status.
- In iOS 27 or later, there is also a Sync Immediately option under Saved to iCloud with a For Today choice, which prioritizes the upload. If you let Photos use cellular data, expect higher data use.
- Turn off Low Power Mode while the first upload runs. Apple notes that Low Power Mode pauses iCloud Photos temporarily, which also pauses the upload.
Check that the setting is saving space
Go to Settings > General > iPhone Storage and give the list a moment to load. The bar at the top shows how much space each category uses, and the app list below shows Photos with its size. Check it once before you turn on Optimize, then again a few days after the upload completes, and compare the two numbers. The walkthrough for how to check your iPhone storage explains what each part of that screen means.
Keep your expectations realistic. Because iOS optimizes as space is needed, a phone with plenty of free room may keep many originals on board. The Photos number tends to drop most when the phone is genuinely short on space, which is exactly when you need it. If Photos is small and the phone is still full, look at the other large apps on the same screen instead.
What changes once your library is optimized
Day to day, the Photos app looks the same. A few things behave differently:
- A short wait on older items: when you open an older photo or video whose original lives in iCloud, the phone may show the smaller version first, possibly looking soft or with a loading indicator, while it downloads the full file. On a slow connection that can take a few seconds, and long videos take longer.
- Offline viewing: without an internet connection you still see every photo, but at the reduced quality, and items that were never downloaded can’t be opened at full size. Before a flight or a trip with poor coverage, open the photos and videos you will want so they download first.
- Editing and sharing: editing a photo, sending it at full quality or exporting it to another app typically makes the phone download the original first. That uses data and a little time, but the result is the full-quality file.
- Data use: the downloads count against your Wi-Fi or cellular data like any other download.
Is Optimize the right choice for you?
For most people with a full phone and room in iCloud, yes. The table below covers the common cases.
| Your situation | Better choice | Why |
|---|---|---|
| Phone is nearly full and iCloud has space for the library | Optimize iPhone Storage | Frees space on the phone without deleting anything. |
| Large-capacity iPhone with lots of free space | Keep originals on the iPhone | No space problem to solve, and everything opens instantly offline. |
| You often edit photos or video away from Wi-Fi | Keep originals, or download the projects you need first | Every edit of an optimized item needs the original downloaded. |
| Library is larger than your iCloud plan | Upgrade iCloud, or clean up the library first | Optimize can’t work until the originals fit in iCloud. |
| You travel with little or no internet | Optimize, but download key albums before you leave | Reduced-quality copies are all that is available offline. |
| You don’t want photos in iCloud at all | Leave iCloud Photos off and back up to a computer | Optimize requires iCloud Photos; there is no local-only version. |
Other ways to cut the space photos take
Optimize is the biggest single lever, but the library itself often has plenty to trim. These steps work with or without iCloud Photos.
Empty Recently Deleted
Deleting a photo does not free space right away. It moves to the Recently Deleted album and stays there for 30 days so you can recover it, still taking up room. To reclaim the space now, open Photos, go to Collections > Utilities > Recently Deleted (in iOS 16 and later the album opens only after Face ID, Touch ID or your passcode), then delete the items.
Before you delete anything with iCloud Photos turned on, know that a deletion applies to every device signed in to the same Apple Account. Apple’s prompt says Delete from All Devices for exactly this reason. After the 30 days, or after you empty the album, the items are gone permanently. The steps to permanently delete pictures from the Recently Deleted folder cover this album step by step, and Apple’s page on deleting and recovering photos explains the 30-day window.
Clear out duplicates and photos you no longer want
In iOS 17 or later, Apple’s Recommended for You suggestions point out things you can remove to save space, and the Photos app can merge duplicate photos and videos so only one copy is kept. Screenshots, screen recordings and long videos are usually the quickest wins. For the basics of selecting and removing pictures, see how to delete photos from your iPhone.
Use the High Efficiency camera format
New photos and videos can be smaller from the start. Go to Settings > Camera > Formats and choose High Efficiency, which saves photos as HEIF and video as HEVC. Most Compatible saves JPEG and H.264 files instead, which work everywhere but take more space. Apple notes the option only appears on devices that can capture HEIF and HEVC. Details are on Apple’s page about HEIF and HEVC media on Apple devices.
Rethink Live Photos and video settings
A Live Photo stores a short video clip with each still picture, so it uses more space than a normal photo. If you rarely play them back, you can turn Live Photos on or off on your iPhone in the Camera app. Recording video at a lower resolution or frame rate in Settings > Camera also cuts file sizes, at some cost in quality.
When photos are only part of the problem, the list of other ways to free up iPhone storage covers apps, messages and other space users.
Keep originals on the iPhone or turn iCloud Photos off
If Optimize does not suit you, you can switch back. Do it carefully, because the result depends on free space on the phone.
Switch to keeping the originals
Return to Settings > [your name] > iCloud > Photos (and iPhone Storage in iOS 27 or later) and choose the option to download and keep the originals on the iPhone instead of Optimize. The phone then downloads every full-size original from iCloud. That only works if the iPhone has enough free space for the entire library at full size, so check Settings > General > iPhone Storage first and free up room if you need to. The download can take hours for a big library; keep the phone on Wi-Fi and power.
Turn off iCloud Photos
Turning off Sync this iPhone stops syncing this phone with iCloud Photos. If the library is optimized, the phone does not hold the originals, so iOS asks what to do with the photos on the device, typically offering to download them or remove them from the iPhone. Read that prompt carefully: removing them from the phone leaves the originals in iCloud, but the phone keeps no full-quality copies. If you want everything on the phone, switch to keeping the originals first, wait for the download to finish, then turn off syncing.
Turning off iCloud Photos on one iPhone does not delete the library from iCloud or from your other devices. If you also stop paying for iCloud+ and your storage drops below what the library uses, new uploads stop, so download what you want to keep before you downgrade.
On a Mac
The Photos app on a Mac has the same pair of choices. In Photos, choose Photos > Settings, click iCloud, then pick either the Optimize option or Download Originals to this Mac. Each device keeps its own setting, so a Mac can hold every original while the iPhone stays optimized. Apple’s guide to setting up and using iCloud Photos covers both devices.
Photo storage questions
Does Optimize iPhone Storage lower the quality of my photos?
Not the photos themselves. The originals stay in iCloud at full resolution, and the phone downloads them whenever you open, edit or share an item at full quality. What you see on the phone before that download is a smaller copy, which can look soft for a moment.
What happens if my iCloud storage fills up?
New photos stop uploading, and the phone can’t swap originals for smaller versions on anything that has not reached iCloud. You will see a notice that iCloud storage is full. Free up iCloud space or move to a larger iCloud+ plan, and uploading resumes.
Does this setting affect photos sent in Messages or saved in other apps?
No. It applies to the Photos library. Pictures stored inside Messages conversations, WhatsApp or other apps count toward those apps’ storage and need to be cleaned up there.
A good next step: turn on Optimize, leave the phone on Wi-Fi and power overnight, then check Settings > General > iPhone Storage in a day or two to see how much space Photos gave back.
Kermit Matthews runs Live2Tech from just outside Philadelphia. He is an IT specialist with over 20 years of experience, from a university help desk to small-business IT, IT management and his own consulting practice, and has written tech guides full time since 2020. Steps are checked against the current software on a real device or the maker’s official documentation. More about Kermit.