How do you say i catch that in slang?

"I catch that" is already pretty slangy! But depending on the context, here are some other ways to say it, with varying degrees of informality:

Informal:

* Got it. (Simple and direct)

* I hear you. (Acknowledges understanding)

* I'm with you. (Shows agreement)

* I feel you. (Shows empathy)

* No cap. (Indicates truthfulness, used more in hip-hop slang)

* Word. (Short for "word up," means agreement or understanding)

* You know it. (Confirms shared knowledge)

More Casual:

* Gotcha. (Short for "got you," used in informal settings)

* You're telling me. (Indicates shared understanding)

* That's right. (Simple agreement)

* I see what you're saying. (Shows understanding of the point being made)

Remember to choose the phrase that best fits the situation and your relationship with the person you are speaking to.