A mobile app developer can be a programmer that develops software for mobile devices. Mobile app developers can create apps for iOS, Android or any other operating system using a variety of programming and UX/UI design skills. Here is a quick overview on the skills that mobile app developers freelancers should have: Programming languages like Java for Android, Swift/Objective C and JavaScript for cross platform development Frameworks for cross-platform mobile app development such as React Native UI/UX design fundamentals Approval process for Google Play and/or Apple App Store Experience with RESTful APIs, RESTful services and third-party library Integrations