One caveat first. The write-up doesn't give client versions, account tiers or a full reproduction script. Treat it as one tester's observations, not a benchmark. Vendor documentation fills in many of the gaps, and I've leaned on it below.
How the test was set up
Abidi built an identical folder on both PCs. It held text files, a Word document, an image and nested folders. He let each service finish syncing and then disconnected one machine. After reconnecting, he waited for the clients to settle and checked both PCs, plus the web interface where one existed.
He also made sure every test file was stored locally, not as an online-only placeholder. That matters because a placeholder test and a real local-file test are different experiments.
Single-editor changes were boring, which is the goal
When only one machine made changes offline, all four tools propagated the edit, rename or deletion after reconnection. The real differences showed up when both sides changed things.
Google Drive has one trap here, and it is the streaming-versus-mirroring distinction. Google's documentation says streamed files are only available online unless specifically made available offline through Drive for desktop. It also says they can only be accessed while the app is running. Mirrored files, by contrast, are stored on your computer and in the cloud, and stay available offline even when the app isn't running. If a file you need turns into a placeholder when the connection drops, that is probably streaming mode, not a bug.
Same file, edited on both PCs
- Dropbox produced the clearest signal. Per Dropbox's help page, a conflicted copy gets the editor's username, the words "conflicted copy" and the save date added to its filename. The last version saved appears as the conflicted copy. Dropbox's advice is to compare both versions and merge them manually.
- OneDrive kept both versions of a non-Office file and tagged the local copy with the device name. Microsoft's sync troubleshooting guidance says for non-Office conflicts OneDrive keeps both versions. The online version keeps the original name, and the local copy gets the device name appended. For Office files, opening the file starts a resolution flow with options such as Save a Copy or Discard. For work or school accounts, Microsoft says OneDrive creates up to 5 conflict versions for non-Office file types.
- Google Drive also preserved both versions, but Abidi found the result less self-explanatory than Dropbox's. Be careful with the documentation here. Google's explicit "keeps both" statement covers the case where you switch from streaming to mirroring into a folder that already holds differing files. It isn't a general promise for every concurrent-edit conflict.
- Syncthing was the most transparent. Its documentation says that when a file is modified on two devices and the content differs, one copy is renamed with a
.sync-conflict-<date>-<time>-<modifiedBy>suffix. The version with the older modification time becomes the conflict copy. Conflict files are then treated as normal files and propagate to other devices, so the evidence shows up everywhere.
One OneDrive nuance is worth knowing. Microsoft's support page on duplicate files with a computer name describes a different cause, stale cached credentials, and suggests clearing the MicrosoftAccount entries in Credentials Manager. So a device-named duplicate is not always a true edit conflict. Check whether you really edited in two places before you blame the sync engine.
Renames and deletes: where the folders got messy
Competing renames made the messiest result. To a sync engine, a rename can look like a delete plus a new file, so two offline machines can come back with two valid names. Keeping both names is annoying, but it beats guessing wrong.
Edit-versus-delete was more revealing. Syncthing's documentation says that if a modification conflicts with a deletion and the deletion wins, the modified data is renamed as a conflict copy. The cloud services add safety nets of their own.
Recovery windows differ by service and plan
The recovery windows are not universal, so check your own account.
| Service | Documented recovery window |
|---|---|
| OneDrive (personal) | 30 days for deleted files |
| OneDrive (work or school) | 93 days, unless an admin changed the setting |
| Dropbox Basic, Plus, Family | 30 days |
| Dropbox Professional, Standard, Essentials, team | 180 days |
| Dropbox Advanced, Enterprise, Education, team Plus | 365 days |
| Syncthing | None by default; versioning is off |
Microsoft adds that Microsoft 365 subscribers can roll back an entire OneDrive to any point in the last 30 days. Dropbox notes that add-ons can extend its window and that data-disposition policies can shorten it.
Windows recycle bin gotcha
For Windows users, Microsoft's restore guidance has a useful detail. Files deleted from a OneDrive folder may be in the Windows Recycle Bin. Files deleted from the cloud, including online-only files, don't appear there. In that case you need the OneDrive or SharePoint web recycle bin.
Syncthing: conflict copies are not backups
Syncthing's versioning is the point most likely to bite people. Its documentation says versioning is configured per folder, per device, and defaults to no old copies being kept. It applies only to changes received from other devices. If you change a file locally, Syncthing can't archive the old version.
Turning on Trash Can, Simple or Staggered versioning sends replaced or deleted files into a .stversions folder inside the shared folder by default. Without that, Abidi's summary holds: it is synchronization, not backup. Syncthing also batches changes, with a 10-second default watcher delay and an extra minute for deletions. A short lag after reconnecting is expected, not a fault.
A practical checklist
- Before going offline, confirm the files you rely on are actually local. On Google Drive, check whether you're streaming or mirroring and whether the item is marked available offline.
- After reconnecting, let every client finish syncing before you touch anything.
- Search for unexpected duplicates: device-named files, "conflicted copy" files and
.sync-conflictfiles. - Compare both versions before deleting either. Word's Compare feature is one option for documents.
- Know your recovery window for your account type and plan.
- On Syncthing, enable versioning if you want a safety net, and understand that it doesn't cover your own local edits.
- Keep a real, independent backup. Deletions propagate, and retention is limited.
Bottom line
In this test, every service passed the minimum bar of not losing both edits. Dropbox was the best communicator, OneDrive had the deepest Office integration, Google Drive was fine once streaming and mirroring were understood, and Syncthing gave the clearest mechanics at the price of more work from you. The lasting lesson is simple: a sync client with no error messages can still be hiding a conflict, and sync is not a backup.