What is Discord, the chatting app tied to classified leaks?

PROVIDENCE, R.I. (AP) — The chatting app Discord, which is one of the most popular ways gamers communicate online, finds itself at the center of an investigation into the leak of classified documents about the war in Ukraine. 

The investigation is unfolding as Discord makes an ambitious push to recruit more users and expand the way they use the versatile app. 

Discord said it is cooperating with law enforcement in the investigation of the leak, which is believed to have started on the site. A Massachusetts Air National Guard member reportedly posted on Discord for years about guns, games, favorite memes and, according to some who chatted with him, closely guarded U.S. secrets. 

WHAT IS DISCORD?