Photo Backup on KnightLi Blog

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.

Using Syncthing on Android: Syncthing-Fork Setup and Photo Backup

Sun, 31 May 2026 12:17:19 +0800

Syncthing Series

On Android, there are two common ways to use Syncthing:

The original Syncthing Android client.
The community-maintained Syncthing-Fork.

Both can work for basic use. For long-term syncing of photos, notes, or documents, Syncthing-Fork is usually the better choice. It offers more practical controls for Android background behavior, battery usage, and network conditions, including Wi-Fi-only sync, selected Wi-Fi SSIDs, and running only while charging.

This article combines general Android setup with photo backup. Photo backup is one of the most common mobile Syncthing workflows, but it should not be configured like an ordinary two-way sync folder.

Why Syncthing-Fork Is Usually Better

Android actively restricts background apps. After the screen turns off, the system may suspend networking, freeze processes, or kill background services. If a sync tool does not handle this well, it may only sync while the app is open.

Syncthing-Fork is more practical for phone use because it can:

Set run conditions.
Sync only on Wi-Fi.
Sync only on selected Wi-Fi networks.
Run only while charging.
Fit Android’s background restrictions better.

This does not mean the original client is unusable. It simply means Syncthing-Fork is better tuned for long-running mobile sync.

Installation Sources

Common sources include:

Google Play
F-Droid
GitHub Releases

Choose the channel you trust. After installation, handle permissions and background settings before pairing devices.

Step 1: Grant Required Permissions

On first launch, focus on two permission areas.

Storage Permission

For file synchronization, Syncthing-Fork must be able to read and write target folders.

Recent Android versions may ask for all-files access or similar storage access. Without it, the app may only see a limited set of folders and fail to read photos, documents, or your chosen sync directory.

Recommendations:

Grant the required file access permissions.
Put sync folders under ordinary internal-storage directories.
Avoid protected system directories.

Useful examples:

1
2
3

/storage/emulated/0/SyncData
/storage/emulated/0/SyncData/Notes
/storage/emulated/0/SyncData/Photos

For camera photos, the common path is:

`1`	`/storage/emulated/0/DCIM/Camera`

Battery Optimization Allowlist

This is the most important Android-specific step.

If Syncthing-Fork is not excluded from battery optimization, Android may kill the sync process after the screen locks. The result is simple: you think it is syncing in the background, but it only moves when you open the app.

Add Syncthing-Fork to the system battery optimization allowlist. The setting name depends on the vendor:

Not optimized
Allow background running
Allow auto start
Lock in background
Allow high background power usage

Many Android vendor builds add extra background and auto-start restrictions. If sync is unstable, check both battery management and auto-start settings.

Step 2: Pair with a NAS or Computer

Syncthing pairs devices by adding each other’s device ID.

Assume the phone is device A and the NAS or computer is device B.

On the phone:

Open Syncthing-Fork.
Open the menu.
Show the device ID.
You will see a QR code and a long device ID.

On the NAS or computer:

Open the Syncthing Web GUI.
Click Add Remote Device.
Scan the phone’s QR code, or paste the phone device ID manually.
Name it clearly, such as Android-Phone or Pixel-Phone.
Save.

Back on the phone, accept the connection request.

At this point, the two devices trust each other, but no folder is synced yet.

Step 3: Receive a Folder Shared from NAS or PC

If the computer or NAS shares a folder with the phone, the phone will show a prompt.

For example:

`1`	`Device NAS wants to share folder Notes`

Add it, then choose a local path on the phone, such as:

`1`	`/storage/emulated/0/SyncData/Notes`

After saving, the phone starts downloading from the NAS or computer.

It is better to create the directory manually first so Syncthing-Fork does not place it somewhere unexpected.

If you sync Markdown notes, be careful with application configuration directories. In Obsidian, .obsidian contains workspace state, plugin settings, and cache. If Android and desktop plugins differ a lot, start by syncing only note content and attachments.

Step 4: Back Up Phone Photos to a PC or NAS

The most common phone use case is backing up photos to a NAS or computer.

Photo backup is different from normal file sync. Most people want new phone photos copied to the NAS, not phone deletions mirrored to the NAS. Treat it as one-way backup.

Recommended combination:

Phone side: Send Only
PC or NAS side: Receive Only

The phone sends photos, and the NAS receives and stores them. Add NAS-side file versioning or snapshots to reduce deletion risk.

Add the Camera Folder on the Phone

In Syncthing-Fork’s folder page:

Tap +.
Create a folder.
Use a clear label such as Pixel_Photos or Huawei_DCIM.
Choose the phone’s camera directory.
Share it with your PC or NAS.

The common Android camera path is:

`1`	`/storage/emulated/0/DCIM/Camera`

Screenshots, WeChat images, or other app images often live elsewhere. Add separate folders when needed:

1
2

/storage/emulated/0/Pictures/Screenshots
/storage/emulated/0/Pictures/WeiXin

Paths vary by Android version, vendor, and app. Confirm with a file manager first.

Set the Phone Folder to Send Only

In the phone-side folder settings, change the folder type from:

`1`	`Send & Receive`

to:

`1`	`Send Only`

This makes the phone the photo source. New photos are sent to the NAS, but NAS-side changes are not written back to the phone.

Syncthing is still a sync tool, not a complete backup system. For a safer setup, also enable NAS-side versioning, snapshots, or independent backups.

Configure the Receiver Path

After saving on the phone, the PC or NAS Web GUI will show a prompt:

`1`	`Device Pixel-Phone wants to share folder Pixel_Photos`

Add it and choose the local storage path.

On Windows:

`1`	`D:\Backups\Phone_Photos`

On Linux or NAS:

`1`	`/volume1/photos/phone`

With Docker, remember to use the container path. If the host mapping is:

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

then the Web GUI path should be:

`1`	`/var/syncthing/photos/phone`

Set the Receiver to Receive Only

On the PC or NAS, set the folder type to:

`1`	`Receive Only`

The receiver will accept photos from the phone but will not send local changes back.

This is an extra layer of protection. Even if you move, edit, or delete files on the NAS, those actions should not directly affect the originals on the phone.

Still, Receive Only is not a replacement for NAS history. Enable file versioning or snapshots on the NAS if the photos matter.

Test with a Small Set First

Do not start by syncing tens of thousands of photos.

Test first:

Put 3-5 temporary photos in the phone album.
Confirm that the PC or NAS receives them.
Add a new photo and see whether it syncs.
Delete one test photo on the phone and observe the NAS behavior.
Only then enable the full album.

Folder type and deletion behavior are easy to misunderstand. A small test avoids expensive cleanup later.

Run Conditions: Avoid Mobile Data Usage

Syncthing-Fork run conditions are very useful on Android.

At minimum, enable:

`1`	`Run only when connected to Wi-Fi`

This avoids syncing large files over 5G or 4G.

If you only want sync at home, restrict it to a specific Wi-Fi SSID. This is useful when the NAS is only reachable on your home LAN.

Charging-Only Sync

If you do not need real-time sync, enable:

`1`	`Run only while charging`

A stable workflow:

Take photos and write notes during the day.
Syncthing-Fork does not keep running constantly.
At night, return home and connect to home Wi-Fi.
Plug in the charger.
Syncthing-Fork starts and syncs the day’s photos and files to the NAS.

This saves battery and fits phone usage better than always-on sync.

For notes that must update quickly, you can skip charging-only mode and keep Wi-Fi-only mode.

Android 11+ Storage Restrictions

Android 11 and later restrict storage more heavily. Some directories may not be reliably accessible, especially:

1
2

Android/data
Android/obb

SD card directories may also be limited depending on vendor, Android version, and file picker authorization.

Recommendations:

Create dedicated sync directories under internal storage.
Do not use app-private system directories as primary sync folders.
For photos, prefer ordinary media folders such as DCIM/Camera.
For notes, use a clear path such as /storage/emulated/0/SyncData/Notes.

Stability matters more than choosing a path that looks native.

Do not sync all of:

`1`	`/storage/emulated/0`

It is too large and mixed, with caches, downloads, app data, and temporary files.

Choosing Folder Types on the Phone

Different scenarios need different folder types.

Two-Way Note Sync

If both phone and PC edit the same Markdown notes:

`1`	`Send & Receive`

Avoid editing the same file on multiple devices at the same time.

Phone Photos to NAS

If the phone mainly sends photos:

`1`	`Send Only`

Use versioning or snapshots on the NAS.

Read-Only Materials on the Phone

If the phone only needs to read files from the NAS:

`1`	`Receive Only`

This works for ebooks, reference documents, or script examples.

Think Through Deletion Semantics

Will deleting a phone photo delete it on the NAS? It depends on folder types and sync state.

To reduce risk:

Use Send Only on the phone.
Use Receive Only on the NAS.
Enable file versioning on the NAS.
Add snapshots or separate backups.

If your real goal is archival storage, sync into an inbox directory first, then let a NAS task copy files into an archive directory that Syncthing no longer manages.

Example:

1
2

/volume1/photos/inbox-phone
/volume1/photos/archive

Syncthing writes to inbox-phone; a scheduled script organizes files into archive.

Common Problems

Sync Stops After Screen Lock

Check:

Battery optimization allowlist.
Background running permission.
Auto-start permission.
Whether Wi-Fi-only or charging-only conditions are active.

Often the issue is Android background management, not Syncthing itself.

Cannot Find the Camera Folder

Use a file manager to confirm the real path. The common path is:

`1`	`/storage/emulated/0/DCIM/Camera`

Third-party camera or editing apps may use other folders.

Sync Is Slow

Check:

Whether the phone and NAS are on the same Wi-Fi.
Whether traffic is going through relay.
Whether 22000/TCP and 22000/UDP are reachable on the NAS.
Whether the phone is in power-saving mode.
Whether there are many small files.

Many small files are slower than fewer large files. After the first sync, incremental sync is usually much lighter.

Deleting Phone Photos Also Deletes NAS Copies

That means your sync relationship is propagating deletions. Syncthing is a sync tool, not a built-in append-only backup tool.

Fixes:

Check folder types on phone and NAS.
Enable NAS-side file versioning.
Add snapshots or independent backups.
Use an inbox directory and archive files outside Syncthing’s control if needed.

Recommended Setup

For Android + NAS:

Install Syncthing-Fork on the phone.
Grant file access.
Add it to the battery optimization allowlist.
Pair phone and NAS.
Put notes under /storage/emulated/0/SyncData/Notes.
Use /storage/emulated/0/DCIM/Camera for photos.
Set the phone photo folder to Send Only.
Set the NAS photo folder to Receive Only.
Enable home Wi-Fi-only sync.
If real-time sync is not needed, enable charging-only sync.
Enable NAS-side versioning or snapshots.

This avoids constant battery drain while still backing up photos when the phone returns home and charges.

Summary

Using Syncthing on Android is not just about installing the app. The important parts are permissions, background behavior, battery settings, and network conditions.

Syncthing-Fork is better suited to long-term phone sync. It can limit sync to Wi-Fi, selected Wi-Fi networks, or charging state, reducing battery drain and mobile data usage.

For photo backup to a NAS, use a one-way backup mindset: phone Send Only, PC or NAS Receive Only, plus NAS-side versioning, snapshots, and independent backups. Syncthing handles transfer; long-term safety still depends on your backup strategy.