About 270,000 users of the MyShake app, which is funded by the California Governor’s Office of Emergency Services, were notified of the earthquake. Most of the 3 million who were notified through Google are Android users who have the alerts preprogrammed into their phone operating system, De Groot said. The alerts gave users up to 20 seconds to prepare for the earthquake, De Groot said.

Source: More than 3 million got early warning in California earthquake – Los Angeles Times