A phrase tacked on to the end of a statement to imply that the information being given is simply a courtesy, when in reality there are specific expectations of you now that you have this information
What Danielle says to guy she's been seeing: Oh, hey I decativated my profile on the dating website, just so you know.

What Danielle REALLY means: You better take your dang profile off the dating website too....NOW!!!!
by Dwad!!!! June 29, 2010
"Here's me being a dick:" or "You're not going to like this but you're not allowed to reply:" are synonymous.
"Just so you know: in the new building there will be no dogs allowed." "Just so you know: I've always hated that sweater."
by T. Z. Müller November 10, 2011
A Minecraft animation where some heterochromic guy chases after his supposedly dead demon girlfriend, killing her in the process.

Basically a suicide mission, but for kids!
"That guy in Just so you Know was a huge simp"