The digital system uses Bluetooth signals from phones to alert people if they've been in contact with someone who's tested positive for the novel coronavirus. The project takes advantage of two of the world's most popular operating systems -- Apple's iOS and Google's Android -- to potentially reach billions of people.
To use the features, people can download the app, called CA Notify, from Google's Play store for Android phones starting Thursday. On iPhones, people can turn on the alerts in their phone settings.
Newsom's announcement makes California the biggest state to adopt the features, first announced in April. The project is a rare public collaboration between the two tech rivals, but some critics have expressed privacy concerns over the potential for abuse and mass surveillance. The companies said they intend to shut down the tools after they are no longer needed to fight the pandemic.
The move comes as several of the most populated counties in California have gone into lockdown as COVID-19 cases surge and health officials worry about capacity in hospitals. The state has 1.3 million cases, and the virus has killed more than 19,800.
"California is facing one of its biggest challenges yet in its fight against COVID-19," Google CEO Sundar Pichai tweeted on Monday.
In another tweet, Apple CEO Tim Cook said "exposure notifications will help slow the spread of COVID-19 and put our neighbors' health first."