When syncing: Replace server data or Replace local data?
- Replace Server Data: pushes your local 2Do tasks up to the sync service. Use this when 2Do has the right data and the server is empty or out of date.
- Replace Local Data: pulls tasks from the server down to this device. Use this when the server has the right data.
- Merge: reconciles both sides instead of overwriting either one, keeping items from each and only duplicating what it can't confidently match. Use this when both the device and the server hold real data you want to keep. On iPhone, iPad, and Mac, the one-shot picker calls it Merge Sync. Android names and availability are listed below.
For iCloud on Android, the same choices are called Keep This Device's Tasks (replace the iCloud copy), Keep iCloud Tasks (replace this device's copy), and Combine Tasks (merge). See iCloud first sync on Android.
Pause before choosing. If your device is empty and you choose Replace Server Data, the empty device can overwrite the cloud copy. Always pause and think about which side has the data you want to keep before confirming. When in doubt, share / export a backup first.
Where to set this any time
Beyond the automatic first-sync prompt, you can pick the next sync's behavior manually whenever you need it:
- iPhone and iPad: Settings > Sync > Next sync action.
- Mac: 2Do > Settings > Sync > Next sync action.
- Android: Settings > Sync setup > Next sync action.
On iPhone, iPad, and Mac, Merge Sync is available for every sync method. iCloud, Dropbox, Toodledo, and CalDAV (iCloud CalDAV and custom) offer the full set: Sync Normally, Replace Server Data, Replace Local Data, and Merge Sync. WebDAV is coming soon and will offer the same set. Todoist and Apple Reminders offer Sync Normally, Replace Local Data, and Merge Sync; they never overwrite their own app's store, so Replace Server Data isn't offered for them.
On those Apple platforms, use Merge Sync only when both sides hold changes you need to keep, or when you are unsure which side is complete. It compares every task one at a time, so it can take a very long time with a large number of tasks. If one side already has the complete copy, use Replace Local Data or Replace Server Data instead. The exception is a complete copy on a device that syncs with Todoist or Apple Reminders: those methods do not offer Replace Server Data, so use Merge Sync there and allow it the time it needs. Merge never deletes to make the two sides match; worst case it keeps a duplicate of an item it couldn't confidently match, which you can remove by hand. For the full description of each action, see Sync overview (Mac) or Sync overview (iOS).
On Android, the choices depend on the sync method:
| Method | Keep data from both sides | Use the account's copy on this device | Replace the account with this device's copy |
|---|---|---|---|
| iCloud | Combine Tasks | Keep iCloud Tasks | Keep This Device's Tasks |
| Dropbox / CalDAV | No Merge choice | Replace data on this device | Replace server data |
| Toodledo | Merge local data with server | Replace data on this device | Not available |
| Todoist | Merge sync | Replace data on this device | Not available |
Every Android method also offers normal syncing. A successful sync resets the next action to normal syncing. See Android replacement choices.
Common recovery pattern
If one device has the complete, current 2Do data and another device is missing tasks or out of sync:
- On the device with the most accurate data, create a backup first.
- On iPhone, iPad, or Mac, use Replace Server Data, except with Todoist or Apple Reminders, where you use Merge Sync. On Android, use Keep This Device's Tasks for iCloud, Replace server data for Dropbox or CalDAV, Merge local data with server for Toodledo, or Merge sync for Todoist.
- Trigger a manual sync and let it finish. Check the resulting data before replacing any other device's copy. Merging with Toodledo or Todoist keeps tasks already on that service; it does not replace the whole account.
- Back up any unique work on each out-of-sync device. On iPhone, iPad, or Mac, set Next sync action to Replace Local Data. On Android, choose Keep iCloud Tasks for iCloud or Replace data on this device for the other methods.
- Trigger a manual sync on each out-of-sync device and let it finish.
Do not choose Replace Server Data on an empty or stale device. That can overwrite the good server copy with bad data.
If no single device or account has the complete copy, keep backups of both sides before proceeding. Android's Dropbox and CalDAV setup does not offer a Merge choice, so do not choose a replacement expecting it to combine the copies.