To check your MasterCard gift card balance online, you can visit the official website of the card issuer or the specific website mentioned on the back of your card. Typically, there's a section on the website dedicated to checking your balance where you'll need to enter your card number and sometimes a PIN or security code. Alternatively, you can use third-party platforms like MyBalanceNowPro which often provide convenient and user-friendly interfaces for checking balances and managing your gift cards. Always ensure you're on a secure and trusted website when entering sensitive information related to your card.