iOS 18 App Lock vs a Photo Vault: Which Is More Private?

iOS 18’s app lock adds a Face ID prompt to the Photos app, but your photos stay in the same library and still sync to iCloud if that’s turned on. A photo vault instead moves chosen photos into a separately encrypted container with its own key. The built-in lock is fine for casual privacy; a vault gives real separation. Plenty of people use both.

What iOS 18’s app lock actually does

iOS 18 added a genuinely useful privacy feature: you can require Face ID, Touch ID, or your passcode to open a specific app, even when your iPhone is already unlocked. Touch and hold the app icon, choose Require Face ID, and from then on the Photos app asks for authentication every time someone taps it. There’s also a Hide and Require Face ID option that tucks an app away in the App Library’s Hidden folder, though that part is reserved for third-party apps.

The best way to picture what this solves is the “hand me your phone” moment. You unlock your iPhone to show a friend a photo, then they start swiping, or they open Photos out of curiosity. With app lock on, they can’t. The lock also keeps that app’s content out of places like Spotlight search, Siri suggestions, and notification previews, so a locked app leaks less around the edges too.

It’s worth being precise about the mechanics, because the name oversells it slightly. Your iPhone already encrypts all of its data at rest using a key held in the Secure Enclave. App lock does not add a second, separate encryption layer on top of your photos. What it adds is an access gate: a Face ID check in front of an app whose data was already encrypted the same as everything else on the device. That’s a real improvement to everyday privacy, but it’s an access control, not a new vault.

There’s one more layer to switch on. With Stolen Device Protection enabled, someone who watched you type your passcode still can’t fall back on that passcode to get past an app lock while the phone is somewhere unfamiliar. In that situation the lock insists on Face ID or Touch ID, which a stranger doesn’t have. It closes the nastiest gap in the built-in lock, the shoulder-surfed passcode, and it costs nothing to switch on.

The Photos app also has its own Hidden album, which iOS keeps behind Face ID by default. That’s convenient, but it’s the same idea as app lock rather than something stronger: a gate in front of photos that still live in your normal library and still sync to iCloud. We get into why that album is weaker than it sounds in why the iPhone Hidden album isn’t actually private.

What a photo vault app does differently

A dedicated photo vault takes a different approach. Instead of putting a lock on the door of the room where all your photos live, it moves the photos you care about into a separate room with its own, different key.

When you import a photo into Arca, it’s encrypted with AES-256-GCM using a key derived from your PIN through Argon2id, a deliberately slow function that makes guessing the PIN expensive. That encrypted copy lives in the app’s own container, separate from your main Photos library. There’s no server and no account behind it, so those photos are never uploaded anywhere and never sync to a cloud. The vault holds only what you deliberately put in it, which is the whole point: a small, chosen set of photos gets stronger, separate protection rather than the whole library getting one shared gate.

Two honest caveats come with that model, and they matter. First, a vault protects only the photos you move into it, not the thousands still sitting in your camera roll. Second, if you import a photo but leave the original in Photos, you now have two copies, and the unprotected one is still right there. Moving a photo into a vault means also deleting the original, or the separation you just created is only half real.

Head to head: the real differences

Both options improve on doing nothing, but they protect against different things. Here’s how they line up.

	iOS 18 app lock	Photo vault (e.g. Arca)
Where photos are stored	Normal Photos library	Separate encrypted container
Separate encryption key	No (uses device encryption)	Yes (key from your PIN via Argon2id)
Syncs to iCloud	Yes, if iCloud Photos is on	No, there’s no server
Granularity	Locks the whole Photos app	Locks a chosen set of photos
Someone with your unlocked phone	Blocked by Face ID prompt	Blocked, and the vault is a separate app
Cost and setup	Free, built in, instant	Requires installing and moving photos in
”Show one photo” without exposing the rest	Hard, it’s all or nothing	Easy, only vault photos are separated

The row that surprises people most is iCloud. App lock changes who can open the Photos app on your device, but it does nothing to the copy of those photos sitting in iCloud, which is still there, still syncing, and still openable from a browser or another signed-in device. If keeping photos off the cloud matters to you, an access gate on one app doesn’t address it at all. This is the same gap we walk through in where to store private photos: the lock and the storage question are two separate decisions.

Where iOS app lock is the right call

None of this makes the built-in lock a bad choice. For a lot of people it’s exactly the right amount of privacy, and it’s free.

• Casual snooping is your main worry. If the realistic risk is a partner, kid, or coworker grabbing your unlocked phone, a Face ID prompt on Photos handles it cleanly.
• You don’t want to manage another app. App lock is one toggle. Nothing to import, nothing to maintain, nothing new to remember.
• You want everything covered, lightly. It gates your entire photo library at once, so there’s no risk of forgetting to protect a particular photo.
• You’re fine with iCloud. If you already trust your iCloud setup and just want a barrier on the device, the lock fits that comfort level.

Used this way, iOS 18’s app lock is a smart default. It closes the most common privacy gap most people actually have, which is someone poking around on a phone that’s already unlocked.

Where a vault makes more sense

A vault earns its place when the built-in lock’s limits start to matter to you.

• You want specific photos truly separated, not just gated. A vault takes them out of the main library entirely and encrypts them with their own key.
• You want no cloud copy. With an on-device, no-server vault, the photos were never uploaded, so there’s nothing to sync, leak, or subpoena from a company.
• You need the “show one photo” case to work. Because only your sensitive photos are in the vault, you can hand someone your unlocked phone, or open Photos yourself, without exposing them.
• You want a plan for being pressured to open your phone. Arca includes a decoy vault, a separate PIN that opens a different, innocuous set of photos, which is a very different protection from a single Face ID gate. We cover that scenario in depth in what to do if you’re forced to unlock your phone.

The trade is effort. A vault only works for the photos you actually move into it, and you have to delete the originals to get the full benefit. In exchange, that chosen set gets real separation instead of a shared lock.

The thing both share: neither is a backup

Here’s a point that catches people out with either option, so it’s worth stating plainly. Locking an app does not back up your photos, and moving them into an on-device vault does not either. In fact, a vault can be riskier for data loss, because those photos now live in one app’s container and nowhere else.

If your phone is lost, broken, or wiped, anything that existed only inside a vault and nowhere else is gone. Privacy and backup are two different jobs. The safe habit is to keep an encrypted backup of anything irreplaceable somewhere separate, which we lay out in backing up private photos without trusting the cloud. Protect the photo, but also make sure a copy survives the phone.

What neither option protects against

Being honest about the ceiling matters as much as the pitch, so let’s name the risks that sit outside what either tool can do.

Neither protects you from copies you left elsewhere. A photo you locked in the Photos app is still exposed if you also texted it, dropped it in Files, or saved it to another cloud. Moving a photo into a vault accomplishes nothing if the original is still sitting in your camera roll. The weakest link is wherever the loosest copy lives.

Neither stops someone who can compel you to open the phone. A person standing over you, or a legal order, can get past a Face ID gate. That specific gap is what a decoy vault is designed for, and it’s why an app lock alone offers no answer to the “unlock it now” moment.

And neither replaces the basics. If your passcode is weak or shared, or the phone is running something malicious that can capture what you type, even strong encryption is undermined at the source. Both tools assume a healthy phone and a passcode only you know. They’re one layer, not the whole wall.

How to decide (you can use both)

You don’t actually have to choose one, and the strongest setup often uses each for what it’s good at.

Turn on iOS 18’s app lock for your Photos app as a baseline. It’s free, instant, and it closes the everyday “someone opened my photos” gap for your whole library. Then, for the smaller set of photos that need more than an access gate, the ones you’d never want on a cloud or exposed in a “let me see that” moment, move those into an encrypted vault and delete the originals.

Think of it as two rings. The built-in lock is a light gate over everything. The vault is a strong box around the few things that need it. Matching the tool to the actual risk, rather than assuming one feature covers every case, is what real privacy looks like in practice, and it starts with being honest about what each option does and where it stops.