If a passcode hasn’t been enabled on your device, it’s worth setting one up to avoid unwanted access – whether by family, a friend – or a stranger.
To do this, open the Settings app and select Touch ID & Passcode, then Set Passcode. From iOS 9 onwards the default passcode is a 6-digit numeric code (older versions of iOS use a 4-digit code). Type in your chosen sequence, and then when prompted type it a second time for verification. The password is then set.
To enable a different type of passcode, tap Passcode Settings from the Set Passcode screen. You can then choose between the old style 4-digit code, or a longer, more complex set of numbers (Custom Numeric) or a limitless string of both numbers and letters (Custom Alphanumeric).
Whatever you choose, you’ll need this code to access the device in the future, so make sure to remember it.
To disable a passcode, open Settings, select Passcode, then Turn Passcode Off. Now enter the passcode to disable it.
How soon?
After setting a passcode, you can also choose how soon it’s needed after locking the device. Tap on Require Passcode and select from the options. A shorter length of time makes your device more secure. Bear in mind that if you have the fingerprint-scanning Touch ID enabled, the only option is to require the passcode immediately.