A free and open-source operating system for smartphones and tablet computers, based on the Android mobile platform. It is the successor to the highly popular custom ROM CyanogenMod, from which it was forked in December 2016 when Cyanogen Inc. announced it was discontinuing development and shut down the infrastructure behind the project. Since Cyanogen Inc. retained the rights to the Cyanogen name, the project rebranded its fork as LineageOS.
LineageOS was officially launched on December 24, 2016, with the source code available on GitHub. Since that time, LineageOS has been described as highly popular and forcibly developed; within 4 months from the initial announcement, LineageOS development builds covered more than 160 models of phone, and over a million users, having doubled its user base in the month February–March 2017.