YouTubers test out Ghost Radar, one of the most popular mobile apps for detecting "ghosts." WSJ's Andy Jordan samples the online amateur reviews.

PARIS - Police revealed Tuesday they had infiltrated and taken down an encrypted chat app called Ghost used by criminals ...

Ghost hunters Roger Pingleton and ... Scientists, of course, denounce the idea. The app, like myriad other devices that claim to detect or communicate with spirits, can not be proven to work.