American Express SafeKey is an easy and free way to further enhance online transaction security when you shop online. An added security measure for online Card transactions, American Express SafeKey only applies to participating online merchants certified by American Express. When making online purchases at these merchants, an OTP will be sent to you to authenticate each transaction. You will receive this OTP via SMS and/or Email using the contact details you have put on the records for your American Express Card. When you checkout at participating SafeKey merchants, an OTP will automatically be sent to your mobile phone number and/or Email address as per our records. As always, please ensure you keep your mobile phone number and Email address updated with American Express for all of your primary, additional, and supplementary Cards. However, if you are shopping at a participating SafeKey merchant and need to update your mobile phone number or Email address, you can do so by a updating your contact details during checkout in a few simple steps to get an OTP sent to your updated contact details in real time for that transaction.