CA Notify is a free service that allows you to find out if you were exposed to COVID-19. You can also notify others if you test positive, while remaining anonymous. Your personal information is never collected, so you and those around you can stay safe.

https://canotify.ca.gov/

California COVID Notify allows users to send and receive notifications of a potential high-risk exposure to COVID-19, in a privacy-preserving manner. The notifications will include instructions on who to contact and next steps to take. The exposure notifications are intended to supplement the conventional contact tracing efforts undertaken by local public health authorities involving contact by a caseworker.