iOS 15.2 allows you to reset locked iPhone without connecting to computer

Once the iPhone is unlocked, erasing and resetting it to its original state is pretty easy. With just a few taps in Settings, you can erase all of your device's content and configuration.

However, so far to reset the iPhone in the locked screen state you need to connect to the computer. First, you need to put your iPhone into DFU recovery mode then connect it to a Windows or Mac computer and then reset it through the iTunes software.

This method is too outdated, so Apple decided to release a new solution from iOS 15.2.

Now, a locked iPhone or iPad only needs a network connection and running iOS 15.2 to reset it without a computer.

After several incorrect password attempts, an "Erase iPhone" option will appear at the bottom of the screen. Just tap it, confirm you want to erase the device, then enter your Apple ID password to unregister your account. Next, the device will reset itself, completely erasing all personal data and returning to the state as it was just shipped.

Without an internet connection, the Apple ID account verification step will fail and the device will not be able to be erased. In that case, you will still have to use the DFU => traditional computer connection method.