The Action button is new on the iPhone 15 Pro and Pro Max, replacing the Silent Mode switch on previous versions and the 15 and 15 Plus. You can launch apps, activate shortcuts, or silence your phone. That's about all you can do.
iPhone 15 Pro – How to Create CRAZY Shortcuts for Action Buttons!
The default option is to turn on silent mode, which is what the previous toggle did. To use the Action button as is, long-press it. (The button on the left side of the phone, above the volume buttons.)
To customize the Action Button, go to Settings > Action Button and select one of the options below.
If you need your camera faster than you can click the app icon, use the Action button as a shortcut. Great for when you're traveling or taking photos at a party.
