The problem it solves
Google's own help page says a personal account includes up to 15 GB of storage in its storage-management documentation. That pool is shared across Drive, Gmail and Photos. When it fills, Google says you won't be able to back up photos or videos to Google Photos, and Gmail stops sending and receiving mail.
That explains the author's motivation. Google One is the paid fix. Syncthing is the free alternative for the camera-roll part of the problem.
Syncthing is not a drop-in replacement for Google's whole backup system. A camera-folder sync does not capture device settings, app data or messages. It also leaves your only extra copy on a PC in your home, not off-site.
What the author set up
- Android: Syncthing-Fork, a community wrapper around Syncthing.
- Windows PC: the open-source Syncthing Windows Setup installer maintained by Bill Stewart.
- Pairing: open the Syncthing web interface on the PC, choose Actions, then Show ID, and scan the QR code with the phone app.
- Direction that worked: sharing the phone's camera folder to the PC went smoothly. His test of a 7.17 GiB photo folder reached a sustained speed of nearly 8 MB/s. That is one person's result, not a benchmark.
- Direction that failed: sharing a PC folder to the phone stalled. The Windows interface showed the message that the remote device had not accepted the folder. After a few attempts he created a new folder on the phone and used that. He blames Android's scoped-storage restrictions. That is his explanation, not a confirmed Syncthing bug.
Corrections worth knowing
The Windows installer is not a service by default
The article says the installer sets Syncthing up as a native Windows background service. That is only true in one install mode.
- Per the project's version history, Setup now defaults to non administrative (per user) installation mode as of version 1.28.0, released December 2024.
- The documentation says that to install Syncthing as a service, you must specify the /allusers parameter on Setup's command line.
- In that mode, Syncthing runs as a Windows service using a local service user account (SyncthingServiceAcct by default).
- The default per-user install instead creates a scheduled task that starts Syncthing at logon. It only runs while that user is signed in.
For a PC that should receive photos while nobody is logged in, the all-users service install is the one you want. It requires administrative rights. The service account must also be able to write to your destination folder.
The AC-power option depends on install mode
The "run only on AC power" choice the author praises exists. The setup project lists a task named "Start automatically only if the computer is running AC power", and it is tied to the current-user logon task. The project's changelog says it was added in 1.27.6 and is disabled by default. You have to tick it during setup. Treat it as a way to cut background activity, not as a guarantee of zero battery use.
The Android app's history is slightly different
The original Syncthing Android repository says the app is discontinued in its README, with the last release tied to the December 2024 Syncthing version. The Syncthing-Fork README says its maintainer no longer publishes it on Google Play. It points users to GitHub releases or F-Droid. It also says another volunteer has announced he will continue Play Store publishing, and leaves readers to decide whether to trust him.
So "get it from the Play Store or F-Droid" is not a single safe instruction. Check the publisher on any Play listing, or use F-Droid.
"Never touches a third-party server" is too strong
Syncthing's security documentation says device-to-device traffic is protected by TLS. Devices authenticate each other by certificate fingerprint, which is the Device ID. Normally your files go directly between devices.
When devices can't connect directly, Syncthing can use volunteer-run relay servers. Relaying defaults to on. The documentation says relays can't read the data, but they do learn device IDs. Global discovery servers also see device IDs and IP addresses. Your files stay encrypted, but a third party can sit in the path.
Syncthing's FAQ also notes a common cause of relay use. When a Windows PC joins a new network, Windows sets the profile to "Public" by default. That often blocks direct connections and forces a relay. Setting your home network to Private is the usual remedy.
The one-way setup, and its limits
By default, folders use Send & Receive. A deletion on one device then propagates to the other. The author's fix:
- On the phone, open the shared camera folder in Syncthing-Fork and change Folder Type to Send Only.
- On the PC, open the web interface, click the folder, choose Edit, stay on the General tab, and set Folder Type to Receive Only.
This matches Syncthing's documentation. A Send Only folder ignores changes from other devices. A Receive Only folder doesn't push local changes out to other devices. The docs describe Receive Only as suited to backup destinations.
Two caveats matter:
- Deletions on the phone still propagate. If you delete a photo from the camera roll to free space, Syncthing sees that as a change and removes it from the PC. Receive Only does not make the PC an archive.
- The project says it isn't a backup tool. Its FAQ says Syncthing is not a great backup application because changes, including deletions, spread to all devices. It adds that you can enable versioning, but it encourages using other tools to protect against mistakes.
If these photos matter, turn on file versioning on the PC side and keep a second copy somewhere else, such as an external drive. Then test restoring a file.
Keeping battery use down
On the phone, the author uses Settings, then Run Conditions. He turned on Wi-Fi only and set power to AC (charging). Syncthing-Fork also documents per-device and per-folder sync conditions. You can limit big media folders to charging and Wi-Fi while letting small document folders sync freely. The project also warns that Android 15 and newer restrict background run-condition monitoring, so behavior may vary by phone and Android version.
Security basics
Syncthing's documentation warns that anyone who obtains a device's TLS keys and config file can impersonate it and reach your synced files. If a phone or PC is lost, remove it from your other devices. If you rely on disk encryption, keep Syncthing's config folder on the encrypted disk too.
Verdict
This is a sensible way to get a free, automatic camera-roll copy onto a Windows PC. You control where the data lands, and it doesn't count against your Google quota. The costs are a fiddly first setup, Android storage and background quirks, and a PC that has to be on.
My advice:
- Use an all-users service install if you want it to run unattended.
- Use Send Only on the phone and Receive Only on the PC.
- Turn on versioning and keep a second backup.