Autofill your username and password in Safari on Mac
With AutoFill, you can easily fill in your previously saved usernames and passwords for websites. You can also have a strong password created for you when you set up a password on a website. Fields where information has been entered for you are highlighted in yellow.
Create a strong password
In the Safari app
on your Mac, when a website asks you to create a password, click the password field.
Click the AutoFill Key button
, then choose Suggest New Password.A strong password is suggested for you, with a yellow background. To decline the suggested password, click the password field, click Don’t Use, then enter a password.
Enter the rest of the required information to create the website account.
If you have iCloud Keychain set up on your Mac, a unique, hard-to-guess password is automatically suggested when you first click the password field.
Autofill a password
In the Safari app on your Mac, do one of the following:
If you previously stored your username and password for the website, use AutoFill to enter the information and sign in. Click in the username field, then choose your username (or use the Touch Bar).
If your Mac or Apple keyboard has Touch ID, you can use Touch ID to fill in your stored username and password and sign in. If the web page has an option to remember your information (such as a “Remember me” tickbox) and you want to use that option, select it before you use Touch ID. If your Mac is connected to an external display while the built-in display is closed, enter the account password for your Mac, then click AutoFill.
Tip: If you use iCloud Keychain to keep information secure on your Mac and other Apple devices, you can use AutoFill to enter previously saved user names and passwords on all those devices.
If there’s no stored username and password for the website, save the information and use AutoFill next time. Enter the username and password, or automatically create a strong password (described below), then click Use Strong Password when asked.
Tip: You can also use your Apple ID and Sign in with Apple to create an account for the website. See Use Sign in with Apple.
If you can’t save a password or autofill a saved password
If you can’t save a password for a website or your password for a website isn’t filled in automatically, try any of the following:
Make sure you selected to autofill passwords: Choose Safari > Settings, click AutoFill, then make sure “Usernames and passwords” is selected.
Check whether you chose to never save the password for the website: Choose Safari > Settings, click Passwords, then unlock your passwords. If a website’s password shows “never saved”, click the Remove button
to remove it from this list. Then click the Add button 
to add the website, your username and your password to the list.Make sure you chose to use Touch ID for passwords: If your Mac or Apple keyboard has Touch ID and you want to use Touch ID to fill in user names and passwords, choose Apple menu
in the sidebar, then turn on Use Touch ID for autofilling passwords on the right. (You may need to scroll down.) See Change Touch ID & Password settings.
How Safari keeps usernames and passwords secure
Usernames and passwords are encrypted in your macOS keychain. They’re also encrypted in your iCloud Keychain if it’s set up on your Mac.
If you remove usernames and passwords in Safari, they’re deleted from your macOS keychain. They’re also removed from your other Apple devices if your Mac and other devices are set up for iCloud Keychain.
For security, set up your Mac to display the login window when it starts up and to require a password after sleep or a screen saver begins. Set up your iPhone, iPad and iPod touch to require a passcode to unlock the screen: Go to Settings > Face ID & Passcode (or Touch ID & Passcode), then tap Turn Passcode On.
Important: Safari autofills your information for anyone who uses your Mac with your user login. It also autofills your information for anyone who uses your other Apple devices, if those devices and your Mac have iCloud Keychain set up.