This is the question that decides whether an alarm app is worth installing at all, and most listicles skip it. An alarm a Focus mode can silence is not an alarm.
Apple's Clock
Alarms set in the Clock app ring regardless of the silent switch and regardless of Focus modes. This has been true for years and remains true in iOS 26. Sleep Focus does not silence them either; that is the entire point of the feature.
The one thing that still applies is alarm volume, set under Settings → Sounds & Haptics. Silent mode does not mute the alarm, but a volume slider dragged to the bottom will make it quiet. Worth checking if your alarm rings but barely, and covered in full in how iPhone alarm volume works.
Third-party alarm apps
Before iOS 26, third-party apps could not match this. They were built on notifications, and a Focus mode could suppress them. That is the historical reason people distrust third-party alarms, and it was justified.
Since iOS 26, apps built on AlarmKit can schedule real system alarms that sound through Silent mode and Focus, with a full-screen alert. Whether any given app has adopted it is usually not stated on its App Store listing, so the safe assumption is that you do not know until you test.
One useful hint: AlarmKit apps must ask permission to schedule alarms. If an app never asked, it is probably not using that path.
The three-minute test
- Set an alarm for two minutes from now.
- Turn on Silent mode using the switch or Control Centre.
- Enable a Focus, ideally Sleep or Do Not Disturb.
- Lock the phone, put it face down, and do not touch it.
- It should ring at full volume with a full-screen alert.
Then do it once more after restarting your iPhone, because surviving a restart is where third-party alarms historically failed. Three minutes total, and it settles the question permanently.
If you would rather work through every failure mode at once, the iPhone alarm reliability check is the full list as a set of things to tick off.
The other things people assume block alarms
Silent mode and Focus get the blame, but the same question gets asked about several other states. For a system alarm, the answer is the same in every case: it rings.
- A locked phone. No effect. Locking has never suppressed an alarm.
- The app closed, or swiped away. No effect on a real system alarm, because the alarm is registered with the system rather than kept alive by the app. This is exactly the distinction that separates the two kinds of alarm app, and it is why the restart test above matters.
- Low Power Mode. Does not disable or quieten alarms. It trims background activity and some visual effects; a scheduled alarm still fires. An alarm that failed on a nearly flat battery almost always means the phone died, not that Low Power Mode intervened.
- Aeroplane mode. Alarms are local to the device and need no connection.
- Headphones or a speaker still connected. This one is a genuine risk, and the exception to the pattern. The alarm rings, but some of the sound may go to the connected device rather than the phone's speaker.
What to do if it fails the test
- Check the app has alarm permission in Settings. This is the most common cause.
- Check Focus settings for any app-specific allowances that were changed.
- Check alarm volume under Sounds & Haptics.
- If it still fails, the app is probably using notifications rather than system alarms. Use Apple's Clock for anything that matters, or switch to an app that passes the test.
Where Mornio sits
Mornio uses AlarmKit exclusively, with no notification fallback, which is why it requires iOS 26.1. That means it passes the test above by design. It also means it cannot run on older iPhones at all, which is a real cost we accepted deliberately.
Run the test on Mornio too. We would rather you trusted it because you watched it work than because we said so.