I have no support/technical question and have seen the support category. (Be aware that direct support questions will be deleted.)
on
Which general topic do you have
I have been running NextCloud AIO and some weeks ago there was an issue where if you update your docker environment then NextCloud could not start. That is since fixed.
When my NextCloud service did not run I was happy to see that I had all my files in my local folder synced via the NextCloud client - all was good and I was happy.
Then when the AOI was fixed I reinstalled AIO, connected my client to the new NextCloud instance and then I lost all my data!!
Luckily I did have a backup.
But my big question is: Why did the client delete the data and not sync it to the server ?
Simply deleting my local data without any notification or option to prevent it is not very nice.
Nextcloud Desktop client is a bi-directional synchronization tool, not a backup solution. This is clearly described in the official documentation, which explains that local and server-side changes are synchronized in both directions.
The documentation does not explicitly describe what happens when the client is connected to a freshly installed or empty server. In practice, when reconnecting to a new instance without an existing sync database, the client has no historical context to determine whether local files should be uploaded or removed. As a result, it may interpret the server’s empty state as a legitimate change and synchronize that state locally, which can lead to deletion of local files without an explicit prompt.
My personal best practice to avoid this is to temporarily move all local data outside of the sync folder before reconnecting the client.
After the initial synchronization completes, I move the data back into the sync folder so they are uploaded to the server instead of being removed.
Do not think I implied that NextCloud is a backup solution.
You mention that it is a bi-directional synchronisation tool - in my mind that means that whatever is in one folder should be synched to the server and only be deleted if it is requested to be deleted and if in doubt, merge or ask - never delete files on a client without asking!
I did try to read the documentation, and I could not find the place where it say that if you connect the NextCloud client to an exiting folder, then all files will be deleted.
The fact that there is not historical context, does not imply that the files should be deleted.
IMO, the NextCloud client should indicate an sync error if it does not know what to do with a file, simply deleting it is plain wrong.
OneDrive wil merge files.
Google drive will merge.
DropBox will copy exiting files.
To the best of my knowledge no cloud solution will delete exiting files if you connect the service to an exiting folder with files.
And once again, I did not blame NextCloud, I simply wrote about my experience to warn others not to do the same mistake as I did!
Glad for clarifying — I did not mean to imply that you were treating Nextcloud as a backup solution either.
My intention was not to debate whether this behavior is ideal or how it should work. I fully understand your expectations, and I agree that from a user perspective, deletion without an explicit decision is surprising.
I shared my best practice specifically because the same thing happened to me in the past. After that experience, I changed how I reconnect clients to a fresh or reinstalled instance to avoid any risk of data loss. That is the only reason I mentioned it — as a practical workaround based on real experience, not as a defense of the behavior.
Your post is valuable exactly because it warns others who might otherwise make the same mistake. That was also my goal in replying.
On a quick search, I didn’t find a related bug report. Perhaps I missed something, but in case there is none, it would be great to let developers know about this issue. If something is so counter-intuitive and leads to data loss, this is a serious issue. In doubt, it could just move files into a subfolder that is excluded from sync, check again with the user what to do, … I don’t know what is the easiest to implement (merging would be the best).
For people in doubt, who check the documentation before, we should maybe add some more detail in the documentation as well?
Well, To be honest, I do not know if it’s bug or ‘by-design’, but I will be happy to create an issue to see if the developers can improve the NextCloud app