Systems and methods for facilitating online payments via an HTML document embedded inside another HTML document on a payee website (e.g., an "inline frame" or "iFrame"). Generally, the iFrame permits a payor (e.g., customer, constituent, donor, etc.) to pay for a transaction (e.g., purchase, utilities payment, fine, donation, dues, etc.) on the payee's website without requiring the payee (e.g., merchant, utilities provider, government entity, non-profit, etc.) to handle the payor's payment data (e.g., credit card information, bank account information, blockchain-based transaction information, etc.). Further, the iFrame permits the payor to pay for a transaction on the payee's website without requiring the payor to leave the payee's website.