This information originates from a member of the MacRumors forum, who previously accurately disclosed details about Dynamic Island on last year's models.

Sources confirm that the Action button will replace the silent switch present on every iPhone model since 2007. While the functionality of the new Action button hasn't been explained, it's likely to be customizable similar to the Watch Ultra, allowing users to set various functions with each press.
Some functions users can assign to the new Action button include: Toggle ringer/silent, Do Not Disturb, Flashlight, Low Power Mode, Brightness mode, Orientation lock, Show Home Screen, Show Lock Screen, Open Control Center, Open Notification Center, Open Camera, Take Screenshot, Record Screen, Run Shortcut, Activate Reachability, Show App Switcher, Show App Library, Shazam, VoiceOver, Magnifier, Background sound.
- Toggle ringer/silent
- Do Not Disturb
- Flashlight
- Low Power Mode
- Brightness mode
- Orientation lock
- Show Home Screen
- Show Lock Screen
- Open Control Center
- Open Notification Center
- Open Camera
- Take Screenshot
- Record Screen
- Run Shortcut
- Activate Reachability
- Show App Switcher
- Show App Library
- Shazam
- VoiceOver
- Magnifier
- Background sound
Most of these functions could already be controlled using Back Tap, an accessibility feature introduced with iOS 14. Back Tap allows you to double or triple tap the back of your iPhone to trigger a specific action, such as turning on the flashlight or taking a screenshot.

Rumors have suggested that the silent switch on the Pro lineup will be replaced by a new button, and the latest information has further solidified that claim. Today's sources confirm that the Action button will continue to function for a period after the iPhone runs out of battery thanks to being equipped with a new low-power chip.
In addition to the Action button, the iPhone 15 Pro models are rumored to have a single volume button that can adjust both volume up and down. Both buttons are expected to have solid-state designs, meaning they won't physically move when pressed and instead provide haptic feedback from an additional Taptic Engine to simulate the sensation of movement, similar to the latest iPhone Home button.
