Y Media Labs employees a 170-person team devoted to creating the best iOS and Android mobile apps and responsive websites. User engagement is important to Y Media Labs, therefore, they start the process of app design by analyzing their client's target audience and then the firm creates a customer journey map. The best mobile app design firm also teaches customers how to read their user-friendly app's analytics, which measure revenue, retention rates and app drop-off points. Y Media Labs has created products for an impressive list of clients, including PayPal, Staples and Western Union. The firm is headquartered in San Francisco, with branches in New York City, Chicago, Indianapolis and Atlanta, Georgia.