After a month of testing on university campuses, California’s governor just announced that the state is launching its COVID contact tracing app to the public this Thursday, December 10th. The app is called CA Notify, and its launch makes California the 18th state (plus Washington, DC) to release a contact tracing app. It’s also the largest to have done so since the technology was announced in April. The first app of its kind was released in Virginia back in August, so it’s been quite a long time coming, especially considering California is home to Apple and Google, the two companies that developed the contact tracing technology the app uses.

Apple CEO Tim Cook and Alphabet CEO Sundar Pichai have tweeted in support of the app:

The app uses the contact tracing API that was added to iOS and Android back in May, and it requires an iPhone with iOS 14.2 or a phone running Android 6.0 or above with Bluetooth Low Energy. Basically, your phone will automatically exchange a private key with another phone if they’re within Bluetooth range. (The key doesn’t contain location or any personally identifying information.) When someone tests positive, they can press a button to send a notification to every other person using the app whose phone virtually bumped into theirs, letting them know that they should get tested and quarantine. If you’re concerned about privacy, it’s worth noting that the exposure notification won’t include any information about who exposed whom or when and where it happened. It will only say that you’ve been exposed.

If you have an Android phone, the CA Notify app will be available on December 10th for download on the Google Play Store. California’s site has a guide for iPhone users, but it’s pretty simple: go to the Settings app then to Exposure Notifications. Tapping “Turn on Exposure Notifications” will let you select California as your region and turn on the tracing. (iPhone owners won’t need a separate app.) It also seems like iPhone users will be able to turn it on before the official launch, as shown in the tweet bellow. I’ve tested it, and it does let you add it, but warns you that “you will not be able to share a COVID-19 Diagnosis with other users until CA Notify is fully enabled statewide”.

Since California is home to the tech companies behind the tracing technology, I’m hoping we’ll see a high rate of adoption. It’s just unfortunate that it’s taken seemingly tech-forward states like California (which is currently seeing a spike in cases) this long to roll out the app. Washington state, the home of Microsoft and Amazon, just rolled out its app last week.

Update December 7th, 5:50PM ET: Added tweet showing how you can turn on exposure notifications early on iOS if you live in California.