The following items could not be synchronized.

[ArZero]

Let me explain the situation. Basically, I’ve been using Syncthing for quite a long time, maybe a year. Everything was working fine. I needed to set a password for the Syncthing configuration page, and that’s when the problem arose. First, I initially entered a password there, and the program seemed to change it, but it didn’t accept the same password when logging in. I changed it to something easier(syncthing generate --gui-password), and everything started working. Great.

Today (maybe a week or two later), I synced with my phone and… the file itself seems to have been transferred, but the program is displaying an error.

No, if they gave me a path like that, I wouldn’t understand it either. LMAO.

So… how I can fix this? I searched GitHub and didn’t see any similar cases.

EDIT: Running on the latest version of Syncthing v2.0.12, on phone v2.0.10

[AudriusButkevicius]

This is a genuine file that it’s trying to sync (hence should exist on the other device), it has colons in the name which are not valid on Windows.

Rename/remove the file, this is independent of every else you did.

[ArZero]

@AudriusButkevicius

has colons in the name which are not valid on Windows.

Rename/remove the file, this is independent of every else you did.

Which one? There is only one file and one hidden folder used by the program. Could it be a bug?

[AudriusButkevicius]

Yes, windows device doesn’t have it, as it’s failing to sync it due to it’s name, so it’s not expected to be there.

The file originates on the other devices, which is where you should look.

[ArZero]

The problem is that there is nothing else besides this file. There is nothing in those two hidden folders except for the old version of the database. But they shouldn’t be synchronized.

[tomasz86 (Tomasz Wilczyński)]

Please post full screenshots of the web GUI from both sides. Make sure to include the folder information unfolded.

[Adhjie (Adi)]

Search windows linux macos android iOS restricted filenames. Windows filename can’t end in period or colon. I usually rename my message media files that end with period with X-Plore to %name.syncthing.EXTENSION (from android to windows).

[ArZero]

UPD: root cause found

I’ve found the actual cause of the issue, and it turned out not to be related to Android, hidden files, or leftover synced items.

The problem was the physical folder name itself.

The folder was named SYNC (e.g. B:\SYNC\). When the folder has this exact name, Syncthing on Windows consistently reports errors like:

CreateFile \\?\B:\SYNC\B:: 
The filename, directory name, or volume label syntax is incorrect.

Important details:

• This happens even with a fresh config

• Even if the folder contains only one valid file

• Independent of Folder ID or Folder Label

• Android had no permission to sync this folder at all

• Renaming the folder to anything else immediately fixes the issue

So the error is triggered purely by the folder being named SYNC. It looks like a Windows-specific path handling / name collision bug.

I’ll close this thread and open a issue with a minimal reproduction.

Thanks to everyone who tried to help — the assumptions were reasonable, but the root cause turned out to be different.

[chaos]

Great job figuring that out @ArZero.

One point of information: One of my Win11 Devices has all of the directories being used as Syncthing Folders under D:\Sync\. So it’s D:\Sync\Work, D:\Sync\Personal, and so on. No difficulties with this whatsoever. But there is no Folder that is associated with D:\Sync\ by itself, in my cluster.