Your computer's a year old? Better buy a new one! ... j/k
|HHJK||Haha, just kidding|
|HHOJ||Ha-ha only joking|
|LJK||LOL just kidding|
|JJA||Just joking around|
|BNR||But not really|
|LOL||Laughing out loud|
Those who are J/K are "just kidding." This acronym is used to indicate a person was previously joking around or messing with you.
J/K is similar to J/P, which stands for "just playing." Either acronym can be written with or without the / character and retain its meaning. These days, because most people type on mobile device keyboards, you'll more often see J/K written as JK.