For added security, I recommend randomly distributing capital letters, digits, and characters throughout the access code. There is no technical limit to the length of the iPhone's alphanumeric code, but the ideal is to have between six and ten characters. Tap Activate password or Change password. To see the options for creating a password, tap Passcode options.
The safest options are the custom alphanumeric code and the custom numeric code. Changing to an alphanumeric password on the iPhone is incredibly easy and anyone can do it. Go to the settings app, tap the Face ID passcode menu &, enter your passcode and select Change Passcode. After setting up a passcode, on compatible models, you can use Face ID or Touch ID to unlock your iPhone (depending on the model).