Most popular APIs: Facebook, Instagram, youtube Xcode, Android Studio, Swift, Objective C, Java, XML, WatchOS, CoreData, CoreAnimation, In App Purchase, In App Billing, Push Notifications, UI (pixel-perfect layout using Auto Layout, SizeClasses, Google Material Design), REST API and SOAP, Convert website to IOS app, Chatting, Video-streaming, Photo editing, Geo location, AWS, Firebase, RxJava, Stripe/Braintree