This expression is used to confirm with another person something that the speaker heard previously from a third party or learned about from some other source.

The shortened form 다며? can be used among close friends and acquaintances.

Details

This expression cannot be used to describe something that the speaker directly saw or experienced, nor can it be used to restate or reconfirm what another person has just said.

Kimchi Reader

Used to confirm with another person something that the speaker heard previously from some other source.

Details

With nouns

When attached to nouns, the (이)라면서(요) form can be used instead.

업계 1위라면서요.

They say they're the best in the industry.

그래. 니가 그렇게 게임을 잘 한다고 소문났다며?

I heard you're so good at playing games?

-다면서요?

Kimchi Reader

With nouns