Alarm Didn't Go Off? Why It Happens and How to Fix It

An alarm that didn't go off almost always failed in one of three ways: it never fired, it fired with no sound, or it rang and stopped before you woke. Each has different causes on Android and iPhone. Beyond Alarm covers all three, and its reliability screen checks Android's settings for you.

The short version:

• Use Beyond Alarm for mornings that matter. On Android it checks the settings that stop alarms, holds the Alarm volume at maximum while it rings, and sets its alarms again after a restart, before you unlock. On iPhone it rings through Apple's AlarmKit, on silent and in a Focus.
• No ring at all? Look for an overnight restart, battery limits on the app, or an alarm set for PM or the wrong day.
• Vibrated or showed, but silent? Check the alarm's own sound and the Alarm volume, then Do Not Disturb on Android.
• Rang, but you slept through? Most clock apps stop by themselves after a few minutes. An alarm that doesn't time out fixes that.
• Then test it: a three-minute alarm, phone locked, face down.

First: which of the three failures was it?

"My alarm didn't go off" covers three different failures, and fixing the wrong one wastes the next morning too.

Beyond Alarm is built so none of these happens. The sections below show where each fix lives.

How to check what happened after the fact

Look for evidence before you reset anything.

1. Did the phone restart? If it asked for your PIN or passcode instead of your fingerprint or face this morning, it restarted overnight. Both Android and iPhone require the code after a restart.
2. Read the notifications. On Android, Google's Clock can tell you why an alarm was quiet. Its help page lists messages such as "Do Not Disturb silenced your alarm" and "Battery Saver may have prevented your alarm from going off".
3. Open the alarm itself. Read the time slowly (7:00 PM looks like 7:00 AM at midnight) and check the repeat days. A weekday alarm won't ring on Saturday.
4. Check the volume. Google's page flags an alarm volume "below 30%" as possibly too low. On iPhone, the alarm follows the Ringtone and Alerts slider in Settings → Sounds & Haptics on iOS 26.

It never fired: the Android causes

Android alarm apps need the phone to let them run at the right moment.

• Battery optimisation and app sleeping. Every maker adds its own layer. Samsung has Sleeping apps, Xiaomi has Autostart, vivo and OPPO have their own background limits. A third-party alarm app you never open is a prime target.
• A restart left the phone locked. After a restart, Android keeps app data locked until the first unlock, so many alarm apps can't set their alarms until then. Why a restart silences alarms is explained in full separately.
• Doze held it back. Android's Doze documentation says standard alarms, even exact ones, are deferred while the phone sits idle. Alarms set as alarm clocks "continue to fire normally".
• Alarms & reminders was switched off. Since Android 12 an app needs this permission for exact timing. Without it, an alarm can arrive late or not at all.

Beyond Alarm's reliability screen checks exact-alarm permission, notifications, full-screen alerts, battery optimisation, the Alarm volume and Display over other apps, and on Xiaomi, vivo, OPPO, realme, OnePlus and similar phones it adds auto-start and unused-app pausing. It gives the phone a score and opens the right page for each fix.

The per-brand checklists

Each maker hides these settings somewhere different. Pick your phone:

It never fired: the iPhone causes

When an iPhone alarm doesn't fire, it's usually the alarm itself.

• A sleep-schedule alarm switched off. The wake-up alarm from Health is separate from Clock alarms, and can be turned off for one night only.
• The wrong time or day. PM instead of AM, or a repeat that skips today.
• The clock was changed by hand. Apple warns that changing the time manually "can affect alarms". Set Date & Time back to automatic.
• Alarm permission refused for an app. A third-party AlarmKit app needs your permission to schedule alarms. On iPhone, Beyond Alarm's reliability screen shows whether it has it.

Our iPhone alarm checklist walks through all nine causes Apple's own pages point to.

It fired, but made no sound

The phone did its job; the sound didn't reach you.

1. The Alarm volume is down. On Android, alarms have their own slider, separate from media and ringtone. If it rings but is too quiet, see why alarms are too quiet on Android.
2. The tone is silent or missing. A tone set to None, or a song or downloaded file that has since been deleted, can play nothing.
3. Do Not Disturb or a Mode muted it. On Android a schedule can switch on at night, and alarms from third-party apps depend on its exceptions. The three ways Do Not Disturb silences an alarm are covered separately.
4. A maker setting. Samsung's Clock has a switch called "Silence alarms when system sound is off". Samsung alarm with no sound covers it and the rest.

On iPhone, Apple says silent mode and Do Not Disturb don't affect the alarm sound, so look at the volume and the alarm's own tone first.

It rang, and you slept through it

If the alarm went off and you didn't wake, no setting above will help. Most built-in clock apps stop ringing by themselves after a few minutes (what "alarm automatically silenced" means), and many let you turn the alarm off with one tap you won't remember making.

If you keep switching alarms off in your sleep, read why you turn off your alarm in your sleep and how to wake up a heavy sleeper.

How to make sure tomorrow's alarm rings

Set an alarm for three minutes from now, lock the phone and put it face down. If it rings at a sensible volume and the screen comes up, the basics are right.

Then check what a three-minute test can't catch:

1. No restart overnight. Turn off scheduled restarts (Samsung's Auto restart, for example) or move them to the afternoon.
2. No bedtime mute. Look at Do Not Disturb, Sleep or Bedtime modes and any routines that run at night, and make sure alarms are allowed.
3. The real alarm is right. AM or PM, the repeat days, and a built-in tone.
4. Battery is unrestricted for a third-party alarm app on Android.

Re-check after any system update. That's when settings like these reset.

Sources

Checked on 9 November 2026.

• Android Help: Set, cancel, or snooze alarms on your Android device
• Android Developers: Optimise for Doze and App Standby
• Samsung Support: Set and edit alarms on your Galaxy phone or tablet
• Apple Support: How to set and change alarms on your iPhone
• Apple Developer: Wake up to the AlarmKit API (WWDC25)