Alarm not going off on Android?
You set it, you saw it in the list, and the next thing you saw was the time you were supposed to be somewhere. This is the most common complaint about every alarm app on the Play Store, including the ones with millions of installs. It is almost never random. There are five causes, and they are worth checking in this order.
1. The phone was restarted
This is the big one. When an Android phone shuts down, the system cancels every scheduled alarm it is holding. It does not restore them. Each app has to listen for the boot event and re-register its own alarms. An app that skips that step looks completely normal — your alarm is still sitting in the list — but nothing is scheduled underneath.
How to tell: did you restart, or did the battery die, between setting the alarm and the morning it failed? If a system update installed overnight, that counts as a restart too.
2. The app was force-stopped
Swiping an app out of the recents list is fine. Using Force stop in Settings, or a "task killer" or aggressive cleaner app, is not: Android then blocks the app from running or receiving anything at all until you open it manually. No app can override this — it is a deliberate system rule.
How to tell: if you ran a cleaner app or hit Force stop, this is your cause. Open the alarm app once and it will work again.
3. Battery optimisation put the app to sleep
Manufacturer battery managers — especially on Samsung, Xiaomi, Oppo, Vivo and Huawei — can put apps into a deep sleep list where they are not allowed to wake the phone. An alarm that needs to fire at 07:00 while the phone is idle needs an exemption, or it fires late, or not at all.
How to tell: the alarm rang, but minutes or hours late. Check Settings → Battery for a "sleeping apps" or "unmonitored apps" list. Note that an alarm app should use Android's alarm-clock scheduling, which is exempt from Doze by design — apps that use ordinary background work instead are the ones that get delayed.
4. Do Not Disturb or a routine silenced it
Do Not Disturb normally allows alarms through, but the exception can be switched off, and Bedtime mode, Focus modes and third-party automation apps can all mute or reroute audio on a schedule.
How to tell: the screen showed the alarm but you heard nothing. Check Do Not Disturb → Exceptions → Alarms, and any bedtime or focus schedule.
5. The volume was changed by something else
On most phones the alarm volume is a separate stream from media, but system routines, car modes and some apps can still lower it. A common pattern is an alarm that has been getting quieter for weeks until it stops waking you.
How to tell: check the alarm volume slider in Settings → Sound. If it is far from the top and you did not move it, something else did.
The check that removes the guessing
All five of these are invisible after the fact, which is why the same argument happens every time: the app says the alarm was set, you say it never rang, and nobody can prove anything. The fix is a record. An alarm app that logs whether each alarm actually fired — and logs it when scheduling fails — turns a suspicion into a fact you can act on.
Wakebell
Wakebell was built around this specific failure. It re-registers every alarm on boot without you opening the app, it uses Android's exact alarm-clock scheduling so it cuts through Doze, it keeps a volume per alarm that other apps cannot lower, and it keeps an alarm history so you can see whether each one rang. It asks for one permission — notifications — and there is no subscription.