Used in an app called 'Vent' for smartphones, it means "Here for You" where the for is '4.'
Person 1 - "oh no i feel so alone"
Person 2 - "H4U"
(I do not reccomend using this in real life speech)
165👍 3👎
It is another way to say "here for you/I am here for you"
Person 1: I feel miserable
Person 2: u knw im H4U <3
21👍 2👎