iPhone alarm not going off? Every fix, in order

Four causes account for the overwhelming majority of silent iPhone alarms. Work through them in this order — each takes under thirty seconds and rules out a whole category of problem.

1. 1Check ringer volume, not media volume. Go to Settings → Sounds & Haptics and drag the Ringtone and Alerts slider up. The side buttons usually change media volume, not the ringer, so the slider can sit at zero while everything else sounds fine.
2. 2Disconnect Bluetooth. If your phone is still paired with headphones, earbuds in a case, a car or a speaker, the alarm may be playing through that device instead of the phone. Turn Bluetooth off overnight and see whether the alarm returns.
3. 3Confirm AM versus PM. Open the Clock app and read the alarm carefully. An alarm set for 6:40 PM looks almost identical to 6:40 AM at a glance, and it is the single most common false alarm-failure.
4. 4Check Focus modes. Settings → Focus → Sleep. Alarms are supposed to bypass Focus, but a custom Focus with an aggressive schedule can still suppress the alert on some iOS versions. Temporarily disable all Focus modes to test.

These are less common but each one genuinely silences alarms. Work down the list.

1. 1Set the alarm sound again. Open the alarm, tap Sound, and select a tone even if one already appears selected. If the sound is set to None — or to a song no longer on the device, such as a track removed from your library or an unavailable Apple Music file — the alarm fires with no audio at all.
2. 2Turn off Attention Aware Features. Settings → Face ID & Passcode → Attention Aware Features. When this is on, the iPhone lowers alarm volume if it detects you looking at the screen. It can misfire and start the alarm far quieter than expected.
3. 3Restart the phone. A restart clears the scheduling daemon and resolves a surprising share of one-off failures. Hold the side button and a volume button, slide to power off, wait ten seconds, power back on.
4. 4Update iOS. Several point releases across recent years have shipped fixes for alarms firing silently. Settings → General → Software Update.
5. 5Check Do Not Disturb While Driving. If it triggers on a schedule or by motion, alerts can be suppressed in ways that surprise people.

There is a recurring iOS defect in which alarms fire on schedule — the alarm appears in the Clock app as having gone off, and the phone may even vibrate — but no sound plays. It is not user error, and it has reappeared across multiple iOS versions rather than being fixed once.

When it hits, the practical mitigations are: keep iOS current, avoid custom song-based alarm sounds in favour of built-in tones, and do not rely on a single alarm for anything genuinely important.

Swapping to an alarm app does not automatically make things more reliable, and can make them worse. It depends entirely on how the app schedules the alarm.

• Apps that schedule alarms in JavaScript or in their own background process depend on that process still being alive at the right moment. The operating system is free to kill it, and does.
• Apps that fetch anything at ring time — ads, remote config, a sound file — fail when the network is down.
• Apps that rely on a standard notification rather than a real alarm inherit every Focus and volume rule that applies to notifications.

Roosta registers alarms with the operating system rather than scheduling them itself, and nothing on the alarm path touches the network. That is why it still rings when the app has been swiped away, the phone has restarted, or there is no signal at all. It is also why we can be specific about this rather than promising reliability in general.