More than 1 million users have activated WA Notify, the new, anonymous exposure notification tool that uses smartphones to help stop the spread of COVID-19, according to the Washington State Department of Health (DoH).

On Nov. 30, WA Notify launched in more than 29 languages. Within the first 24 hours, more Washington residents opted in than any other state using this technology. As of Dec. 4, the number of phones with WA Notify accounted for more than 19 percent of the number of Washington adults.

By adding the free notification tool to their smartphones, Washington residents will be alerted if they spent time near another user who later tests positive for COVID-19. WA Notify uses privacy-preserving technology jointly developed by Google and Apple and works without collecting or revealing any location or personal data, according to the DoH.

When voluntarily activated, phones with WA Notify use Bluetooth technology to exchange random codes with the phones of other users they are near. It does this without revealing a user’s identity or location. Users who test positive for COVID-19 can enter a verification code provided by public health into WA Notify, so that other users who have been near them within the last 14 days can be anonymously alerted and take appropriate action.