Used in over 50 countries, CommCare (www.commcarehq.org) is the most widely adopted, technically advanced, and evidence-based mobile platform for low-resource settings. CommCare is easily customizable, open source, and supports frontline workers (FLWs) across 200+ projects in over 50 countries. FLWs use CommCare to track and support their clients with registration forms, checklists, SMS reminders, and multimedia. Mounting evidence indicates that this leads to improved frontline worker performance, better reporting, and better client practices and education. CommCare is the only platform for FLWs that is open source, supports longitudinal client tracking, is specialized for low-literate users, runs on Java and Android phones, runs offline, integrates SMS for performance improvement, and has an application builder designed for non-programmers. CommCare is also used to build rapid diagnostic tools and medical reference libraries, allowing users to flag critical cases to appropriate parties. Features include: Counseling messages Supports multiple languages Data collection Interactive multimedia Branching logic GPS Integration Runs on Android and Java feature phones Offline usage and storage Web-based reporting SMS-enabled