You can turn down the alarm volume on your iPhone through the Sound menu in your settings. Here are two ways to do it.

Open the Clock app and go to the "Alarms" tab, then select the alarm you want to edit. Tap the "Sound" option and scroll down to choose a new preinstalled sound or tap "Pick a Song" to choose a song ...

Your alarm should sound when your iPhone is on vibrate mode, regardless of whether the ringer is turned on or off. Here's how ...

For anyone who doesn't like waking up to a jarringly loud alarm, this hidden iPhone alarm feature promises a more gentle way ...