How to Sync iPhone Photos to a PC or NAS with Syncthing

Sun, 31 May 2026 12:21:54 +0800

Syncthing Series

Using Syncthing to sync photos on an iPhone is quite different from doing the same thing on Android.

The reason is simple: iOS is more locked down, and the official Syncthing project does not provide a first-party iOS client. To use the Syncthing protocol on an iPhone, you usually need a third-party compatible client.

There are two common choices:

Mobius Sync: a popular option with an experience close to a native app. Some features may require a paid unlock, so check the current App Store description.
FSync: a free and open-source Syncthing client for iOS.

If your goal is to sync the iPhone photo library to a PC or NAS, Mobius Sync is the more common choice. The steps below use it as the example.

Understand the Limits on iOS First

On Android, Syncthing-Fork can run for a long time through a background service, run conditions, and battery optimization exemptions. iOS does not allow third-party sync tools to run in the background without limits.

This means:

Do not expect it to sync 24/7 like a NAS.
After the app goes into the background, the sync window may be short.
For large photo batches, it is best to open the app manually and let it finish.
iCloud optimized storage may affect whether the original photo files can be read.

So on iPhone, Syncthing is better treated as a “open the app periodically to sync photos” workflow, rather than a fully invisible real-time background sync service.

Step 1: Install the Client and Grant Permissions

After installing Mobius Sync from the App Store, handle these permissions carefully the first time you open it.

Notifications

It is recommended to allow notifications. They can show sync status, connection status, and error messages.

Local Network Access

This permission is very important.

iOS separately asks whether an app may access the local network. If you deny it, the iPhone may not be able to discover your PC, NAS, or other Syncthing nodes on the LAN.

If you denied it by mistake, you can enable it again in iOS Settings.

Photo Library Access

If you want to sync photos, you must allow access to the photo library.

The recommended choice is:

`1`	`Full Access to Photos`

If you only grant limited photo access, Mobius Sync may only see the selected photos, and newly added photos may not be synced later.

Step 2: Pair the iPhone with the PC or NAS

Syncthing pairing still works by exchanging device IDs.

On the iPhone:

Open Mobius Sync.
Go to Settings.
Open Device ID.
Keep the QR code screen open.

On the PC or NAS:

Open the Syncthing Web UI.
Click Add Remote Device.
Scan the QR code on the iPhone, or enter the device ID manually.
Give the device a name, such as My-iPhone.
Save.

Return to the iPhone, wait for the connection request, and tap Accept.

At this point, the iPhone and the PC/NAS trust each other, but the photo library has not been shared yet.

Step 3: Create a Photo Sync Folder on the iPhone

iOS does not let you choose a path like /DCIM/Camera directly in the same way Android does. Mobius Sync provides special support for the system photo library, so you need to choose the photo-library folder type.

In Mobius Sync:

Switch to Folders.
Tap + in the upper-right corner.
Create a new folder.

Important fields:

Folder Type: choose Camera Roll.
Folder Label: use an easy-to-recognize name, such as iPhone_Photos.
Folder ID: you can keep the generated value, or use a stable English ID.
Folder Path: keep the default so the client can bind to the iOS photo library.

Then, in the Sharing section, select the PC or NAS you just paired.

Step 4: Set the iPhone Side to Send Only

Photo sync is usually “phone sends to NAS”, not a two-way editing workflow.

So on the iPhone side, set the folder type to:

`1`	`Send Only`

This makes the iPhone responsible for sending photos out, without accepting reverse changes from the PC or NAS.

This reduces the risk of accidental operations. For example, when organizing the backup folder on the computer, you usually do not want those changes to affect the iPhone photo library.

Still, remember that Syncthing is a sync tool, not a complete backup system. For long-term photo safety, you should also use NAS snapshots, file versioning, or an independent backup.

Step 5: Receive Photos on the PC or NAS

After saving on the iPhone, the Syncthing Web UI on the PC or NAS will show a prompt:

`1`	`Device My-iPhone wants to share folder iPhone_Photos`

Click add.

Set the storage path.

On Windows, it may look like:

`1`	`D:\Backups\iPhone_Photos`

On Linux or NAS, it may look like:

`1`	`/volume1/photos/iphone`

If Syncthing runs in Docker, enter the path inside the container. For example, if the host mount is:

`1`	`- /volume1/photos:/var/syncthing/photos`

Then in the Web UI, use:

`1`	`/var/syncthing/photos/iphone`

Set the Receiving Side to Receive Only

On the PC or NAS side, it is also recommended to set this folder type to:

`1`	`Receive Only`

This makes the receiving side accept photos from the iPhone, without syncing local changes back to the iPhone.

It is a second layer of protection:

iPhone side: Send Only
NAS side: Receive Only

Both ends are configured around one-way backup, which better matches a photo archive workflow.

The Reality of iOS Background Sync

iOS is strict about background execution. Even with correct settings, do not expect Mobius Sync to keep running silently in the background all the time.

Common behavior:

Sync speed is normal while the app is open.
It may keep syncing for a short time after going into the background.
After a while, the system may pause or limit it.
Location changes, system scheduling, or short background windows may wake it again.

The most reliable practical workflow is simple:

After taking many photos, open Mobius Sync manually.
Keep the phone awake, or avoid locking the screen too quickly.
Wait for the new photos to finish syncing.
Then close the app or lock the screen.

If you are used to doing a photo backup every few days, this approach is fairly reliable.

Avoid iCloud Optimized Storage Problems

If the iPhone has enabled:

`1`	`Optimize iPhone Storage`

iOS may keep only thumbnails locally while the original files remain in iCloud. When a third-party sync client tries to read photos, it may not be able to get the full originals, causing failed syncs, skipped items, or waits while iOS downloads the files.

The better setting for sync backup is:

`1`	`Download and Keep Originals`

The path is usually:

`1`	`Settings -> Apple ID -> iCloud -> Photos`

If the phone does not have enough storage and you must use optimized storage, you may need to open the relevant photos in the system Photos app before syncing, so the iPhone downloads the originals from iCloud first, and then start Mobius Sync.

Tips for the First Large Photo Sync

The first time you sync an iPhone photo library, there may be thousands or even tens of thousands of photos. Do not rush to finish everything in one pass.

A safer approach:

Sync a small number of photos first for testing.
Confirm the NAS path is correct.
Confirm the folder types are Send Only / Receive Only.
Confirm the receiving side will not affect the iPhone in reverse.
Then start the full sync.

During the first sync, it is best to:

Keep the iPhone plugged in.
Keep Wi-Fi stable.
Keep Mobius Sync open in the foreground.
Keep the NAS or PC online.

When the photo library is large, the sync may take a long time. That is normal.

Recommended Configuration

A stable iPhone photo sync setup looks like this:

Install Mobius Sync on the iPhone.
Allow notifications, Local Network access, and full photo library access.
Exchange device IDs between the iPhone and NAS.
Create a Camera Roll folder on the iPhone.
Set the folder label to iPhone_Photos.
Set the iPhone-side folder type to Send Only.
Set the NAS receiving path to /volume1/photos/iphone.
Set the NAS-side folder type to Receive Only.
Enable file versioning or snapshots on the NAS.
Open Mobius Sync manually every few days to complete sync.

If you rely heavily on fully automatic background photo backup, iOS will be more troublesome than Android. The system restrictions make it difficult for third-party sync tools to behave like an always-on background service.

Summary

An iPhone can join the Syncthing ecosystem through Mobius Sync or FSync, and sync photos to a PC or NAS.

The key differences on iOS are background limits and photo-library permissions. During setup, allow Local Network access and full photo access. Design the folder types around one-way backup: iPhone Send Only, NAS Receive Only. If iCloud optimized storage is enabled, also check whether the original photos are truly available locally.

For photo archiving, the most stable workflow is to open the client periodically to sync, then let the NAS handle version retention, snapshots, and long-term backup.

IPhone on KnightLi Blog