When editing a cloud-hosted document via Synology WebDav the OnlyOffice editor does not detect or warn the user when the connection to the document server is lost. The editor continues to accept input, but all unsynchronized edits are lost once the session is closed or refreshed.
Steps to reproduce:
Open a document stored in the cloud
Start editing.
Disconnect the network (e.g. disable Wi-Fi) or stop the OnlyOffice DocumentServer process.
Continue typing for a few minutes — the editor shows no warning.
Reconnect or reload the page.
All changes made while disconnected are lost.
Expected behavior:
The editor should immediately detect the loss of connection.
It should display a clear “Connection lost / Offline mode” warning.
Local unsaved edits should be cached and recoverable once the connection is restored (similar to Google Docs or Collabora Online).
Actual behavior:
No visible warning is shown.
The status indicator still shows “Saved” or no status change.
All edits made during disconnection are lost permanently.**
Environment:
OnlyOffice DocumentServer: 9.1.0.167 (x64 exe)
Integration: Synology NAS
No Reverse proxy
Network conditions: LAN and Wi-Fi drop simulated
Additional notes:
This behavior can cause severe data loss for users working with unstable connections. It would be highly useful if the editor implemented:
a clear offline detection mechanism (WebSocket/HTTP heartbeat),
a visible “offline” indicator,
and an autosave cache or recovery option for local unsynced changes.
Suggested enhancement
Implement an offline detection system similar to:
navigator.onLine status in browsers
WebSocket ping/pong with a visible reconnect indicator
Local temporary file caching (so users can recover unsaved changes)
Please provide more information about your environment:
version of Desktop Editors;
how Desktop Editors are connected to Synology WebDAV;
version of Synology WebDAV.
It seems that incorrect category is set to the topic, because the description of the issue clearly refers to Document Server. If Document Server is used, please share its installation type and version too.
Version of Desktop Editors: Community version 9.1.0.167 (x64 exe)
Synology DSM Version 7.2.2
How Desktop Editors connect to Synology WebDAV: Only for Windows 11 users. WebDAV access is via File Explorer > Add network location. The link then appears permanently under My PC. There were never any problems like the ones described here with the previously used MS Office 2021.
The Synology NAS is operated by a company, and WebDAV access is only available to company employees.
For this purpose, a dedicated access point has been set up via the File Explorer function “Add network location” and configured with a username and password.
Users can then access the server’s directory using File Explorer and open and edit Office documents stored on the NAS by double-clicking them.
Is there a documentation on that from Synology? Adding a location implies using certain protocols, some of which are not enabled by default. I’d like to see how to configure Synology to work via WebDAV to run some tests.
The server supports “DavDepthInfinity,” which allows access to and deletion of files even with deep path lengths or subfolders—even in complex directory structures.
Access logs (transfer logs) can be enabled to track who accessed which files and when.
In short: WebDAV behaves like a file server over HTTP/S—NAS shares can be mounted practically like network drives, and files can be directly opened, moved, deleted, etc.
But this is no Synology issue!
The problem can be reproduced with any WebDAV server: OnlyOffice doesn’t detect that the connection to the server has been lost. Clicking “Save” appears to execute, but it doesn’t save anywhere, not even locally for safety!
As a workaround, it would help if OnlyOffice offered a setting to perform local backups at definable intervals. Then at least all the work on the document wouldn’t be lost.
The problem is worse than expected. OnlyOffice doesn’t even notice that a client>server network connection via SMB is interrupted and saves the file to nirvana.
Ldap Client (SMB) opens document on the file server
Then I unplug the Ethernet cable
Edit the document and click Save
OO takes a few seconds longer to save and then continues to display the document for editing without an error message.
If I close the document, all changes made are lost.
It couldn’t be worse!
No problem!
First we found the problem in WebDav (by https).
Later, we discovered that even with SMB2/SMB3, OnlyOffice is unable to handle a lost connection to the server.
There appears to be no error handler for the situation where a document is opened and edited in the cloud or on a file server, and then the connection is interrupted.
In any case, no warning message appears; it seems you can still save and close the document. This results in the loss of all changes.
Thanks for the reply. Just to make sure that we are on the same page: you have mentioned Document Server in your original topic:
However, the category is set to Desktop Editors. Can you please specify which one is actually being used? There is a big difference in the way they operate with connected storages per se.
Suggested enhancement