How Do I Change My Lock Screen Password?
However, you may choose to change it at a later date.
Here’s how to change it.

On your iPhone, tapSettings.
slide in your existing passcode.
input your old passcode.

key in your new passcode.
TapPasscode Optionsto choose different types of code.
input your new passcode a second time.

Wait for the passcode to be updated.
How Do I Change My 4 Digit Passcode on My iPhone?
Here’s how to change it.

Four digit passcodes are easy to guess, so Apple recommends you use a more complex passcode.
Your passcode is now a 4 digit entry rather than anything longer.
How Do I Change My Password on This Phone?

Here’s how to do it.
The process is different if you are trying to tochange the password for your Apple/iCloud account.
This may also be called Face ID & Passcode or Touch ID & Passcode depending on your iPhone model.
It can be a mixture of letters and numbers.
Enter it a second time.
Your passcode is now a password made up of letters and numbers.
Why Can’t I Change Passwords on My iPhone?
Here’s a brief look at the common reasons.
The only way to regain access is to erase your iPhone with a computer or with recovery mode.
FAQ
If you use Gmail, you canchange your Gmail password on your iPhonefrom the Gmail app.
Tap the hamburger menu >tweaks>your email address >Manage your Google Account>Security>Password.
Then confirm your current password, slide in your new password, and tapChange Password.
Go toSettings>Phone>Change Voicemail Passwordand update the password box with your new code.
TapDonewhen you’re finished.
Tochange your Twitter password, fire up the Twitter app and tap your profile picture.
Then selectSettings and privacy>Account>Login and security>Password.
put in your current password, your new password, and selectConfirm passwordwhen you’re done.
Go toSettings>Your_Name>Password & Security>Change Password.