IKR is a short written form of “I know, right?” You use it when someone has just said something you already feel is true, and you want to agree in a warm, slightly excited way — not a cold “I already knew that,” but “Yes! That’s exactly it.” It lives in texts, comments, and chat. You would not put it in a school paper. People often give it a line of its own, sometimes with an exclamation mark or a few extra letters (IKR!!!!). Though actually, the “right?” on the end is doing real work: you are not only agreeing, you are inviting the other person to keep sharing the feeling.