To begin changing your iPhone password, open the Settings app. Scroll down until you find Touch ID & Passcode. Choose this option and enter your current passcode when prompted.

Next, scroll down again to find the Change Passcode option. After pressing this option, you’ll again be asked for your old passcode. After entering it correctly, you’ll be asked to input your new passcode. Note that there are additional advanced options that let you set up an alphanumeric passcode or a four-digit passcode if you press Passcode Options. 

Once you’ve entered your new passcode, you’ll be asked to verify it. Input your new passcode again, and you’ve now updated your Apple iPhone password. Don’t forget it!

If you’ve forgotten your Apple iPhone password, there’s no straightforward way to get a reminder sent to you or to reset the passcode. You must wipe your iPhone, which unlocks it but deletes all the data on your device. However, if you’ve made a recent backup, you can restore your data from iTunes or iCloud.

To perform the reset, you need a computer with iTunes installed. If you don’t have access to this, you can take your iPhone to an Apple Store or authorized partner, who can reset your phone for you.

The process to erase an iPhone differs slightly by the version number. Start by disconnecting your iPhone from the computer.

For iPhone 6s and earlier, as well as first-generation iPhone SEs, hold down the Top or Side button until a slider appears on the screen for powering off your device. Drag the slider to power off your phone. While holding down the Home button, connect your phone to the computer. This will load the recovery screen and you can erase your iPhone’s data.

For iPhone 7 models, hold down the Side button until a slider appears on the screen for powering off your device. Drag the slider to power off your iPhone. While holding down the Volume down button, connect your iPhone 7 to the computer. Follow the instructions on the recovery screen to erase all iPhone data.

For the latest models (iPhone X or later, iPhone 8, iPhone 8 Plus, and iPhone SE second generation), hold one of the volume buttons and the Side button at the same time until a slider appears on the screen. Drag the slider to power off your iPhone. Now, while holding down the Side button, connect your phone to your computer. After a few moments, the recovery screen will appear on your iPhone and you’ll be able to erase all data.