How turn iPhone 15 to vibrate on silent mode

There is a doohickey on the side (Silent Switch) to set the Silent Mode ON. The other way to set the Silent Mode ON is to access the Control Center (Pull Down from Top Right of Screen).

To ensure that your iPhone vibrates when Silent Mode is set to ON, open Settings ➡️ Sound & Haptics ➡️ Haptics: Set this to Play in Silent Mode.

Axel F.

The iPhone 15 has a Ring/Silent switch on the left side. See: iPhone 15 - Apple Support

The iPhone 15 Pro has an Action button on the left side. It can be used to change to Silent mode. See: iPhone 15 Pro - Apple Support and Use and customize the Action button on iPhone 15 Pro and iPhone 15 Pro Max - Apple Support (SA)

To vibrate when in silent mode, go to Settings > Sounds & Haptics > and set Haptics (near the top of that screen) to "Play in Silent Mode" or "Always Play."