  On social media algorithms for content promotion, accounting for users
preferences, might limit the exposure to unsolicited contents. In this work, we
study how the same contents (videos) are consumed on different platforms --
i.e. Facebook and YouTube -- over a sample of $12M$ of users. Our findings show
that the same content lead to the formation of echo chambers, irrespective of
the online social network and thus of the algorithm for content promotion.
Finally, we show that the users' commenting patterns are accurate early
predictors for the formation of echo-chambers.
