CyanogenMod (/saɪˈænoʊdʒɛnmɒd/ sy-AN-oh-jen-mod; CM) is a discontinued open-source operating system for mobile devices, based on the Android mobile platform. It was developed as free and open-source software based on the official releases of Android by Google, with added original and third-party code, and based on a rolling release development model. Although only a subset of total CyanogenMod users elected to report their use of the firmware, on 23 March 2015, some reports indicated that over 50 million people ran CyanogenMod on their phones. It was also frequently used as a starting point by developers of other ROMs.