In-app purchase has become an essential monetization model for app developers. Consumers and developers alike face an array of payment options, including credit card, carrier billing, digital wallet (e.g., PayPal), and virtual currency. With a growing volume of in-app purchases, both sides want to reduce transaction friction. This report examines needs from consumer and developer perspectives and analyzes the pros and cons for different payment options for digital in-app purchases. This report projects in-app purchase volume and transaction value for the U.S. market.