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 use Nextcloud Hub 26 Spring (online), the Nextcloud iOS app (iOS 27), and the Nextcloud macOS app (macOS 15.x).
Here’s my question: As far as I know, if I have a file stored in a cloud, whenever I edit it on any device, the change is visible on all devices. Is that correct?
If I edit the same file—but not at the same time—the file’s content on the other devices remains unchanged. This means I have a different version of what is essentially the same file on each device, even though it’s stored in the “Files” folder (online) on my server.
How can I ensure that a file on the server is synchronized across all devices?
Are you talking about files that are edited through the Nextcloud app? Or are talking about files somewhere on your phone/Laptop that you want to sync with Nextcloud?
Whenever you change a file on any location (web user interface of the server, iOS app or macOS app), the changes should be reflected everywhere else afterwards. That is the basic expectation and goal of a synchronization solution like Nextcloud. If it doesn’t, then something is wrong.
Now, there are a myriad of things that can go wrong. And for Nextcloud it is even harder and more complicated, because unlike the big tech brands it is decentralized and people have not just very different devices but also server deployments which often enough are not right.
The best would be, if you could describe with specific steps what you do, what you expect and what actually happens.
NextCloud per se is a cloud file storage. If no sync client is used, but you edit a file inline using the web client, everyone would work with the current version.
If you are on your laptop/pc or phone and edit files locally there then you need an app that does the automatic download if somebody else changes a file where you have a local copy and does automatically upload if you change the local file.
Regarding the Phone things can either get more complicated when you want to automatically sync for example pictures you take. The phone saves those to a separate location, but the Nextcloud apps can be configured to sync specific local folders on the phone to specific folders in the Nextcloud. - But this is a general topic for whatever cloud-file-sync tool/service you use.
So therefore - we need more input regarding your particular problem.
If it doesn’t, then something is wrong.