Exposure notification technology pilot

California COVID Notify app logo

California COVID Notify is currently only available as a pilot test to students, faculty and staff at UC San Diego and UC San Francisco.

The California Department of Public Health (CDPH) and the Department of Technology (CDT) in partnership with the University of California are pilot testing the use of exposure notification technology through the California COVID Notify system. This privacy-preserving technology has the capability to quickly notify users who may have been exposed to COVID-19 and may reduce the spread of this disease in our communities. This pilot helps us learn more about how exactly it works and its potential for helping us slow the spread of the virus to keep each other safe.  

Through this pilot, CDPH and CDT will evaluate the technology and its implementation to determine whether to offer the program to all Californians.  

California COVID Notify, which uses the Google Apple Exposure Notification technology, was selected because it was designed with privacy as a key consideration. See Privacy Policy.  The system does not use location information or collect, store or transmit any personal information at any time. Use of the app is entirely voluntary.  

Watch this video to learn more about the Google Apple Exposure Notification technology. (Also available in Spanish.)

How it works

California COVID Notify uses Bluetooth technology to quickly notify users who have likely been exposed to COVID-19. This may help you reduce the risk of infection for your friends and family and help slow the spread of the virus in California.

How it works notify icon

1. You opt in

California COVID Notify users will be asked to opt in to the notification system.

How you opt in icon

2. Anonymous keys are generated

When you opt in and the Bluetooth is on, your smartphone will generate and transmit anonymous keys (long strings of random characters). These keys can’t be used to identify your location. Keys change every 10-20 minutes to further preserve your identity and privacy.

Anonymous keys generated icon

3. Keys are exchanged

Whenever you carry your phone with you and are near other people also using the system, your phone and theirs exchange these privacy-preserving anonymous keys. This is a passive process that works in the background once you opt in. It does not drain your battery or use data.

Your phone will record the day that the anonymous keys were received, the duration of the signal, and the distance between the two phones (using Bluetooth signal strength as an approximation). These keys are stored on your phone for 14 days, then automatically deleted.

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4. Recent keys are checked

Several times a day, your phone downloads a list of all the anonymous keys associated with positive COVID-19 cases, and checks them against the list of anonymous keys it has encountered in the last 14 days.

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5. When a match is found

If you have a matching key, the system runs a mathematical calculation developed by epidemiologists using the date, duration, and signal strength to assess your level of risk. You will be notified of an exposure only if the calculation meets a pre-specified risk threshold. If you receive a notification, you will be directed to instructions on what to do next and how to keep yourself and the people around you safe. 

If you ever test positive for COVID-19, you can choose to share your anonymous keys with other app users to notify them of a possible exposure. Sharing this information helps others protect themselves and stops the virus from spreading. To do this you will get a verification code from a medical provider, lab, or public health authorities that will allow your anonymous keys to activate notifications to other users. The verification code is required to ensure that only anonymous keys of someone with a verified positive test are shared. When the other users are notified, they will receive a message that they have had a possible exposure to COVID-19 with the date of that exposure. The positive user’s identity or phone number is not shared, but it is possible that it could be guessed based on the exposure date.

See our Privacy Policy.