Hugh McQuaid / ctnewsjunkie

An anonymous smartphone app available to Connecticut residents aims to alert users when they have potentially been exposed to the coronavirus, Gov. Ned Lamont announced Thursday.

The app, called COVID Alert CT, uses bluetooth capabilities developed by Google and Apple to trace the user’s proximity to other users. If someone with the software tests positive for the virus and enters a code into the program, the app will anonymously alert any other user who has spent more than 15 minutes within six feet of that user during the past two weeks.

Similar apps have been rolled out in 10 other states since the spring. Lamont said they are more effective in areas with high user participation.

“I urge you to do this. I urge you to do it now. It is exponentially more effective if each and every one of you download this app,” Lamont said. “If only 5% of your friends do it, you’re not going to be noticed. If 90% of your friends do it, you’re that much safer.”

In a Friday Tweet, Josh Geballe, Lamont’s chief operating officer, said more than 300,000 users activated the app in less than 24 hours of operation.

“Great job Connecticut, please continue to spread the word,” Geballe said.

The Connecticut app is available to both Apple and Android users. During a Thursday press briefing, the governor joked about the ease of the installation process. “Even I could do it. That tells you something.”

Other states have reportedly struggled to achieve high adoption rates of their apps. Geballe said Connecticut’s closest participating neighbors like New York and New Jersey are still in the first couple months of their programs.

Geballe said the architects of the software were aware that some users would be skeptical of the apps in large part due to privacy concerns.

“Just to be clear: the app is not tracking your location, it’s not tracking any personalized information about you or the people you’re in contact with. It’s completely anonymized,” he said.

Users who are alerted by the app to a possible exposure will be urged by the software to get in touch with a contact tracer, to get tested, to quarantine. The app will not automatically alert contact tracers, he said.

The software is also not meant to replace “old fashioned” contact tracing, but rather to complement it, he said. Even if adoption rates in Connecticut are modest, Geballe said it may help keep some residents safe.

“If we can identify even a few dozen people who’ve had close contact that otherwise wouldn’t have been aware, and break some of those chains of transmission, it will help,” he said.