Start with folder already synced

How can I start handling a large folder with Syncthing which is already identical (or nearly so) on both sides? Just deleting one side and resyncing would take way too much time and bandwidth. But in my prior experiments I could get nothing else to work to convince Syncthing there is no conflict.

Thanks for your help,


If the folder is really identical, Syncthing shouldn’t sync anything and just mark the two sides “Up to Date”. If there are additional files on either side, then they will be merged and synced to the side where they’re missing.

However, if the files are supposed to be identical, yet Syncthing marks them as not, then you should check whether things like permissions, filesystem-dependent timestamp differences (e.g. the recent issue on the forum about timezone problems on FAT32 in Linux), extended attributes and ownership (if enabled to sync), etc. between the two sides are different.

Basically, first please provide details about the operating systems involved, filesystems, etc. Screenshots from the Web GUI after adding the folder on both sides would be very welcome. Please also include any error messages you see.

One side is my Mac Big Sur desktop (apfs, journaled), the other side is Android 12, on the external sdcard (so VFAT I think).

Reading your reply carefully, I see you mention timestamps. Will those matter if the file content is found to be the same?

To see this actually happening I’ll have to set up a mock test case - no way I’m going to test this on my real files.

– Ian

Yes, if the content is really the same Syncthing will only exchange metadata. It may look for a long time like it is copying data, but it actually is only exchanging metadata.

If you don’t check any of the boxes for “ownership” and “extended attributes” that should minimize conflicts.

I suggest you start by creating the “sync folders” on both sides; ensure that the options and the folder id are identical and let them complete the first scan.

Connect the two devices without sharing the sync folders.

Once the folders have completed a scan (they will show status “Unshared” in orange), edit the sync folders to share the folder on each side. That will minimize the time the two sides think they are out of sync. You should see the “out of sync” files list diminish to zero fairly quickly.

  • I haven’t experimented, so this last step might not produce the desired result or could be counter-productive: before sharing both folders, set them both to “receive only”. That should allow them to compare and inform you if they are out of sync.
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