Abstract: This document describes methods and systems of on-device real-time translation for media content on a mobile electronic device. The translation is managed and executed by an operating system of the electronic device rather than within a particular application executing on the electronic device. The operating system can translate media content, including visual content displayed on a display device of the electronic device or audio content output by the electronic device. Because the translation is at the OS level, the translation can be implemented, automatically or based on a user input, across a variety of (including all) applications and a variety of content on the electronic device to provide a consistent translation experience, which is provided via a system UI overlay that displays translated text as captions to video content or as a replacement to on-screen text.