Updated
You set the alarm. You saw it turn on. And it still did not make a sound. If that has happened to you, you are not careless. A phone has a handful of settings that can silence an alarm without telling you, and most of them look fine the night before.
Here is what actually causes it, and how to check each one tonight instead of finding out at 9:03 tomorrow.
The silent switch is not the whole story. On iPhone, ringer volume and media volume are two different things. If your ringer and alert volume is turned all the way down, the alarm can play at a volume you will never hear, even with the physical switch off silent. Check Settings, then Sounds and Haptics, and nudge the Ringtone and Alerts slider up.
Focus and Do Not Disturb schedules. A Focus you set once, whether Sleep, Work, or a custom one, can run on a schedule you have long forgotten. Alarms are supposed to break through, but a misconfigured Focus, or a third party alarm app that is not allowed to bypass it, can end up muted. Worth opening Settings, then Focus, and reading what is actually scheduled for tonight.
Audio routing. This one is sneaky. If your AirPods or a Bluetooth speaker are connected, the alarm can play there instead of on the phone speaker. AirPods on the nightstand, phone across the room, and the alarm rings into an empty earbud.
Low Power Mode. Overnight, Low Power Mode can throttle background activity. It rarely kills a standard alarm, but combined with an app that relies on background scheduling, it adds risk.
On Android, it is often the manufacturer. Samsung, Xiaomi, and others add their own battery management on top of Android. After a system update or a reboot, those settings can quietly stop an alarm app from running. If your alarm broke right after an update, this is the usual suspect.
The frustrating part is that none of this is visible the night before. The alarm is on. It looks set. You cannot see that the ringer is down or that Focus will mute it until the moment it fails.
That gap is the reason we built Snora. Snora is an alarm you set like any other. It reads the settings your iPhone lets an app see, such as notification permission, and if one of them would stop your alarm, the home screen shows one line that opens that setting. Volume, Focus, and Bluetooth are not visible to apps, so those stay your own check. It is not a score and not a promise about your morning. The alarm and the check are free, and no account is needed. With Snora Plus, an AI calls you at alarm time and talks with you.
Whatever you use to wake up, the fix is the same. Check the ringer volume, read your Focus schedule, and make sure the sound has somewhere to actually play. Do it once tonight, and you will know before you close your eyes.
FAQ
Will my iPhone alarm still go off on silent?
Yes, the built in iPhone Clock alarm is designed to ring even when the Ring and Silent switch is set to silent. That switch mutes incoming calls and notifications, but the alarm runs on a separate path and still sounds. What can override this is a ringer volume set all the way down, so open Settings, then Sounds and Haptics, and raise the Ringtone and Alerts slider.
Why is my iPhone alarm silent even though it is turned on?
The usual cause is a setting that mutes the sound without touching the alarm itself, most often a ringer volume turned down in Settings, then Sounds and Haptics. A Focus or Do Not Disturb schedule can also mute a third party alarm app that has not been allowed to break through. Connected AirPods or a Bluetooth speaker can send the sound away from the phone speaker as well, so the alarm plays somewhere you cannot hear it.
Does Do Not Disturb stop my alarm from ringing?
No, Do Not Disturb and Focus are built to let the standard Clock alarm ring through. The exception is a third party alarm app that has not been given permission to bypass Focus, which can end up muted overnight. You can review what is scheduled for tonight in Settings, then Focus.
How do I make sure my alarm will ring before I fall asleep?
Check the settings that can quietly mute an alarm before bed rather than at the moment it fails. Raise the ringer volume in Settings, then Sounds and Haptics, read your Focus schedule in Settings, then Focus, and disconnect AirPods or a Bluetooth speaker so the sound has somewhere to play on the phone. An app like Snora reads the permissions your phone exposes and shows a line on the home screen when one of them would stop your alarm, while you can still fix it.