A new web-based tool is helping clear the air over longstanding confusion about the differences between isolation and quarantine as they relate to COVID-19. The U.S. Center for Disease Control and Prevention (C.D.C.) recently unveiled a “Quarantine and Isolation Calculator” meant to help most Americans better understand when they are safe to return to public settings after a COVID-19 exposure or infection. This comes months after the public health agency last revised its quarantine and isolation guidelines, which were criticized for being too confusing over the rhetoric used to describe when either scenario would be applicable. Although the tool should provide more clarity about C.D.C. guidelines, the agency warns that it should NOT be used by anyone who is moderately or severely immunocompromised.