Four Brisbane teenagers have been charged over the alleged rape of a male friend with what is understood to be a beer bottle.

The victim, 19, only became aware of the alleged rape after a video was posted on social media days after the alleged attack on Australia Day.

The video is then believed to have been posted again six weeks later.

The alleged victim made a complaint last month.

Police said three 19-year-olds and a 21-year-old were charged with rape on Friday.

Two of them were are also charged with distributing prohibited visual recordings.

They are due to face the Brisbane Magistrates Court later this month.

According to Seven News, the alleged assault occurred when the victim had passed out after a party in Kedron, in Brisbane's north.

The alleged victim only became aware of the rape when the teenager who posted the video online sent him a link to the post.