How Sync In Background Works
When Sync in Background is enabled, a silent push notification is sent to all devices that are linked to the same iCloud/Dropbox account as soon as changes have been uploaded. This silent push notification informs Due on each device to fetch any changes from Dropbox/iCloud, cancel any outdated notifications, and schedule new ones.
On macOS, as long as your app is running (doesn't need to be in the foreground), it should sync within seconds after changes have been uploaded on another device. If you're experiencing problems on the Mac, please see this support article.
On iOS, it is less straightforward. Because apps do not actively run in the background on iOS, we need to depend on iOS to wake up the app in the background in order to sync your data.
If Background Sync Is Not Working on Your iOS Devices
- Ensure that the 'Sync in Background' switch is enabled in Due > ☰ [Side Menu] > Sync. If it is already enabled, toggle it off, then back on again.
- Ensure that 'Background App Refresh' is enabled in iOS Settings > General > Background App Refresh > Due.
- Force quit then relaunch Due on all of your iOS devices.
- If you also use Due on macOS, relaunch Due on your Mac as well.
Background Sync Will Not Work Under Some Circumstances on iOS
iOS can choose not to wake an app up despite receiving a silent push. There are three main reasons:
- Apps that are manually force quit will not be woken up in the background.
- If you disable 'Background App Refresh' in iOS Settings > General > Background App Refresh > Due, background sync cannot work.
- Finally, a more complicated reason is that iOS has the final say on whether—and how soon—an app is woken up, even after receiving the push notification. This depends on a variety of factors, including: how often you launch Due on the device,* your current battery life, whether you're plugged into power, whether you're on Wi-Fi or cellular, etc.
* This also means that if you've restored your device or set up a new device, the frequency that iOS wakes Due up may be affected because iOS has to relearn how frequently you use Due.
Apple has this to say about the background notification technology:
Important
The system treats background notifications as low priority: you can use them to refresh your app's content, but the system doesn't guarantee their delivery. In addition, the system may throttle the delivery of background notifications if the total number becomes excessive.
To Determine If iOS Is Choosing Not To Wake Due Up
If the steps above didn't help, you can run this test to determine whether the issue is on Due's side or iOS's side:
- On the iOS device (device A) that is experiencing the problem, leave Due running in the foreground.
- Make a change on another device (device B, iOS or Mac), then sync and wait for upload to complete.
- Within seconds after the upload has completed on device B, Due on device A should automatically indicate that it is 'Checking for updates' and sync the new data.
If this is happening as described, this indicates that Due has correctly pushed the update out to all devices, but iOS has chosen not to wake Due up when it is in the background.
It can sometimes take minutes or even up to an hour before iOS decides to wake up an app, usually in response to other push notifications or other scheduled background app refresh from other apps, in order to conserve battery on your device.
Suggestions To Encourage iOS to Wake Due Up More Often
- Launch and use Due on the device more frequently. To train iOS to wake Due up in the background more frequently on a device, try launching it on that device 1–2 minutes after making changes on another device. After a few days, iOS should learn that you use Due often and expect iOS to wake Due up in the background to refresh for new content.
- Enable Incremental Sync on all devices. Incremental Sync optimizes sync to be more energy-efficient and use less bandwidth, which should encourage iOS to wake Due up in a timely manner.
- Avoid having low battery level on the device.
- Keep the device plugged in.
- Connect the device to a Wi-Fi network.
But ultimately, the final call on when and whether to wake up Due to complete the background sync depends on iOS.
Use Shortcuts Automations To Keep Due In Sync (Due 26.3 or later)
Starting with Due 26.3, Due includes a Shortcuts action called Sync and Refresh Notifications. By combining it with Shortcuts Automations, you can have it run automatically throughout the day, so your data and notifications stay up to date without having to open Due. For setup instructions, see Keeping Due in sync across your devices with Shortcuts Automations.
Suggestion To Mitigate The Impact Of Background Sync Delays
If Due is still not waking up often enough to sync changes made on other devices, consider disabling Auto Snooze on the device(s) you're less likely to have with you. For example, if you mainly use your iPhone to mark reminders complete, you could disable Auto Snooze on your iPad in Due > Settings > Alerts & Badges > Auto Snooze. This prevents your iPad from continually alerting you to reminders you've already marked complete on your iPhone when background sync hasn't caught up yet.