What does xx mean in texting?

ok so me and my crush were texting for about 9 hours yesterday from when school day ended until we went to sleep. when we said goodnight for like the 4th time i put goodnight xx and then he replyed goodnight xx back what exactally does xx mean when you put it with goodnight as "goodnight xx? help!
Update: thanks everyone! ps i already knew it meant kisses but i just wasnt too sure so thanks this makes me so happy!
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