Why your alarm stops working after a phone restart
This is the single most common way an alarm app fails, and the reason it is so confusing is that nothing looks wrong afterwards. The alarm is still in the list. The toggle is still on. It simply is not scheduled any more.
What Android actually does
Scheduled alarms live in the system's alarm manager, in memory. When the phone powers off, that goes with it. Android does not persist them for you and does not restore them on the next boot. Instead it broadcasts a signal when the device finishes starting, and every app that had alarms is expected to listen for it and schedule its own alarms again.
If an app does not declare that receiver, or declares it but crashes, or has been put to sleep by a battery manager, nothing is re-registered. The alarm row you see in the app is only a database record — the app is drawing what you saved, not what the system is holding.
Things that count as a restart
- Powering off and on.
- The battery going flat.
- A system update installing overnight.
- A crash and reboot.
The last two are the nasty ones, because you may not know they happened.
A related case: force stop
If you force-stop an app — from Settings, or with a "cleaner" app — Android blocks it from running or receiving broadcasts until you open it manually. In that state it will not even receive the boot signal. This is a deliberate system rule and no app can work around it. Swiping an app out of the recents list is not the same thing and is harmless.
Test your alarm app in two minutes
- Set an alarm for about five minutes from now.
- Restart the phone and leave it on the lock screen.
- Wait.
If it rings, the app re-registers on boot. If it does not, no setting on your side will fix it — the app has to. It is worth testing before you rely on it for something that matters.
What a correct app does
- Registers a boot receiver and re-schedules every enabled alarm as soon as the device starts.
- Uses Android's alarm-clock scheduling, which is exempt from Doze, rather than ordinary background work.
- Re-registers again whenever you open the app, as a second line of defence.
- Records the result, so a failure is visible instead of silent.
Wakebell
Wakebell does all four. Alarms come back after a reboot without opening the app, scheduling is exact, opening the app re-registers everything anyway, and the alarm history shows whether each alarm rang — including a note when registration itself failed.