How can I keep one task list synchronized across my devices?

Choose one task app as the home for the list, then sign in to it with the same account on each device. For Microsoft To Do, Microsoft’s instructions specifically say to use the same account on every device; they also say tasks stored on Exchange Online sync to Outlook Tasks. [S1]

Start with a small check: create a harmless test task on one device, then open the app on your other devices and see whether it appears. Remove the test task afterward. This confirms your setup without relying on a memory of which account or list you used.

For a dependable routine, pick one app as the authoritative list. If you keep a second list, decide exactly what belongs there—for example, a temporary shopping list—and avoid treating both apps as equally complete task records. Otherwise, an item can be updated in one place and left stale in the other.

Before moving anything, compare the lists and copy over only the tasks you still need. A transition note could say: “From [date], new and changed tasks go in [chosen app]. Check [old app] only for items not yet moved.” That is a planning aid, not an app feature.

Do not assume every app handles offline changes the same way. The supplied Microsoft To Do guidance explains account sync, but it does not establish what happens to offline edits or how conflicting edits are resolved. [S1]

A cautious workflow is to note which item you changed and avoid editing that same item on another device until the phone is back online. Reopen the app when connected and check whether the change appears before treating the list as up to date. If the app displays a warning or offers versions to review, pause and read the choices rather than dismissing it.

Suppose, as a hypothetical example, you mark “Book a repair appointment” as done on your tablet while offline, then change its wording on your computer. When both devices reconnect, do not assume one edit automatically wins. Check the app’s conflict notice or help instructions, compare the versions, and keep the version—or versions—that preserve the information you need.

Google Keep’s help describes one specific case: editing the same note on multiple devices while one is offline can produce a conflicting-edits notification. It says users can review the versions and choose one to keep or keep both. [S2] That evidence is about Keep notes, not a general rule for task apps.

For a simple sync check, open the same list on a second device after an important change and look for the updated item. If it is missing, check that both devices use the intended account and list, then consult the app’s guidance. Microsoft says To Do checks for updates every five seconds, but that timing applies to To Do, not every service. [S1]

Test the ordinary path: add an item on one device and confirm it appears on another. Then check the app’s own guidance for offline use and conflict handling; the supplied sources do not establish those behaviors for task-list apps generally. For a deadline you cannot afford to overlook, use a reminder or backup method you already trust rather than assuming synchronization alone will alert you.

A copyable setup note: “Main list: [app and list name]. Account used: [account label]. Devices checked: [device names]. Offline-change rule: reconnect and verify before editing the same item elsewhere. Conflict rule: review the app’s versions or instructions before choosing.”