App internationalization is crucial for mobile developers as it enables their apps to be accessible to a global audience without requiring significant engineering changes or overhauling infrastructure. It involves designing an app that can handle various languages and regions, making it easier to localize later on. The process differs between iOS and Android platforms, with cross-platform frameworks also having specific approaches. To support multiple locales, developers need to separate content from code, avoid hardcoding values, keep audio and video files on the server, and use utility tools for formatting values and units of measurement. Testing localized versions is also essential to ensure app usability. By incorporating internationalization into mobile CI/CD workflows, developers can make their apps more accessible to a broader audience.