Android
Set Alarm Auto-Silence Duration auf Android
By default, an Android alarm keeps ringing until someone dismisses it manually. If the phone is left unattended, that can mean minutes of uninterrupted noise, which drains the battery and disturbs anyone nearby.
The Silence after setting inside the Clock app controls this behavior. It defines a fixed duration after which a ringing alarm stops automatically, even if nobody touches the device.
To change it, open Tap on Clock ➔ Open the menu ➔ Open the settings ➔ Tap on Silence after ➔ Choose an option. Pick a shorter interval if you usually forget your phone at home, or a longer one if you tend to sleep through short alerts.
This setting only limits how long the alarm sound plays. It does not snooze or dismiss the alarm entry itself, and it does not affect notification sounds from other apps.
If your real problem is that the alarm does not ring loud enough or skips entirely, check the alarm volume and Do Not Disturb exceptions instead. Those live in separate sound settings, not in the Clock app's silence timer.